Please excuse me, I probably am repeating what someone else has said... but I can't find that shiny guide anywhere so I don't know if this is in it:

Anyway, on the GTS site it says that supposedly breeding pokemon traded through GTS will have a higher chance of producing shinies. Has anyone confirmed this and does anyone know the likelyhood of this happening?

This does have some credibility. There's a breeding technique called "The Masuda Method" which says that if you breed a foreign Pokemon with one from your game, it hightens the odds of eggs being hatched. There's a Thread about it on here somewhere. Let me go find it.

EDIT: Found it.