I seem to have terrible luck when it comes to finding random encounter shinies! People say the odds are better in the friend safari but I don't think that's the case, I think it's just a matter of there only being the 3 Pokemon in each safari so the rate at which you encounter wild Pokemon, especially a specific one you're looking for is increased, and X and Y do have a higher shiny rate overall than previous games! The shiny I found wasn't random luck, it was more like determination! Seeing everyone else having such luck in the friend safari I went in with lantern (for illuminate ability) holding a smoke ball and a couple other Pokemon and hunted for like 3 days before finally finding that one, so for me the odds don't appear to be any better!