I'm more or less a programmer (something like 60-80% of my time is programming, or programming related) and vegan.
Lets run over the programmers checklist:
1) Caffine. Plant derived, so that's ok.
2) Coffee. Check
3) Pizza. Easy enough to get them to skip the cheese.
4) Guranine. Again, plant derived. 
Are more programmers vegan? Out of all the comp-scientists I know (a lot!) (and I'm excluding this board) I can't place anyone as being vegetarian.
Now, I think that there is a a little self selection going one. The internet, although generally avilable, has a higher than real life proportion of geeky types, programmer, sys-admins etc. Therefore, veg*ns in these professions are more likely to be noticed, particularly if internet surveying is used. For example, I'm on some other boards, and computer people are highly represented on those boards too.
 Ok, this was ment to be funny. I don't think it worked.