hi id just like to mention a few things regarding left handed violinists as i am one ( and also the conversion process one might undertake).
firstly, i attempted to learn the instrument the traditional way but found that i couldnt develop a fluent bowing technique adequate to make me feel like i was making sufficient progress. it never occurred to me that it might even be possible to play left handed as id never seen nor heard of a single lefty violinist in existence. personally i write left handed, i play sports with a mixture of both right and left orientations so its not unnatural for me to use my left hand.
after approximately 4 years of collecting dust i decided one day to dig out my violin and investigate whether converting the violin to left hand would be viable after the reallisation that i might be better suited using my left hand as the bowing hand due to my existing preference for writing, playing tennis with the left etc . after a few searches (courtesy of that wonderland of commerce that is ebay) i purchased a peg shaver, 4 new pegs, and a special tool to re-ream the holes so that the pegs could be reversed (a lot of care is needed to be taken when re-reaming holes) . the pegs i notice definately need to be reversed so that i can avoid knocking the peg when playing notes close to the scroll on the fingerboard when playing the e string. in the "right handed" placement the peg knocks the 4th finger making it impossible to play F / F# without hitting wood. as for the bridge it is simply reversed so it isnt at all an issue (minor shaving when required). the curvature of the fingerboard is uniform from what ive read so another obstacle is successfully overcome. unfortunately from what ive read the soundpost is definately an issue but doesnt impact on the sound quality to the the detriment of the instrument too much (although if anybody believes this not to be the case let me know). i definately enjoy the sound from my converted violin as opposed to a custom made left handed "GLIGA" that ive also bought since, so although the soundposts position might incrementally improve the sound, in a general sense i really dont see the need to pay a luthier to rip the top off just to attend to the alignment of the soundpost.
left handed players arent being difficult or desire to be different simply for the attention (or at least im not) which seems to be the opinion of a few who have replied to various lefty threads and a certain lady ive dealt at a local music store (even though im roughly half way through completing practical/theoretical grades for possible university entrance). its a little patronising to be asked whether you really "have to" play left handed, especially if your quite a few shades more developed than simply "enthusiastic beginner". if i could play right handed i would and ive definately not appreciated having to labour through the extended path ive currently taken to get where i am. the amount of time wasted to reallise that im orientated in a particular fashion would definately of been better allocated to practice.
as for a few issues that seem to polarise people in regards to southpaws, i really dont see why people think orchestras cant accomodate left handed players.
statistically, depending on whose data you obtain the total population of left handers accounts for somewhere between 8-15%. even taking the larger number into account that would mean (all things fair and equal) that a little under 1 in 6 left handed people should potentially be making up the numbers (obviously at 8% that would increase the ratio to roughly 1 in 12). if we take the instruments in question that pose an issue in regards to bowing - violin (1st and 2nd), cello, viola and double bass it is quite possible to place the statistically probable number of leftys on the end of each row without having to redesign the entire layout significantly.
the only problem seems to be the violas wedged in between the 2nd violinists and the cellists. i would envisage an extra gap of 1-2 metres would need to be made to accomodate the left handed viola players.
a 1-2 metre wide gap of concert hall space isnt a sufficient argument to prohibit someone playing in an orchestra!
another reason that people allege is true for not allowing left handed violinists into the club is because it doesnt look very nice to have violinists bowing in different directions which is also quite amusing. as far as i was concerned sound is received through those ear receptacle devices not through visual means. if your simply not satisfied with the sound of the live orchestra due to the appearance of a particular violinists bowing you might be better served sitting at home with your headphones on listening to the orchestra in question playing some dreary lament whilst watching the fashion channel on cable. that way even if one of the orchestras players is left handed you can avoid being visually offended by his/her playing by staring at scantily cladded whisps sauntering down a runway at milan fashion week.
and anyway if you disagree with vioinists being left handed barracks got all our southpaw backs. we obviously mean business !!!!

in answer to a few specific posts in this thread
jurianbai - no need to correct the bridge. the strings get swapped as well so its quite effortless. the only issues are swapping pegs overs and the soundpost which as ive mentioned would need a specialist to attend to. this is a little outside of my limited expertise.
standswithafiddle - i dont know why you would try to force someone to do something that comes unnaturally. personally my current teacher was a little apprehensive about teaching me since i was the first left handed student she'd ever taught but ive been taking lessons for about 2-3 years now and although we'd occasionally confuse each other it really hasnt been a significant issue. if your students are left handed they're more likely to develop a fluent bowing style faster with their dominant hand. depending on how reliant your left handed students are on their left hand, you may have curtailed their development by forcing them to attempt to use the weaker and less coordinated of their hands. i hope you reconsider your policy of making these students play only right handed as it may be prolonging the learning process and hindering their enjoyment. its also potentially making your job more arduous and less enjoyable.
jhansen_violin - id agree with most of what you said except for their being no disadvantage for left handers.
in a mechanical sense theres obviously no disadvantage but there still reigns this deluded belief that its a nuisance for orchestras and at best a novelty.
like i mentioned previously if their was proportional representation in orchestras in regards to left handed players the numbers would reflect more appropriately, but they dont and thats no advantage i know of.