if your about to create a hopefully commercially successfull game, could other companies patent actually be a problem?

Yes, definitely. I don't have any links for you offhand, but it should be easy to google and find a bunch of articles.

One popular example is Carmack's Reverse. So yeah, patent issues could be problematic.

Here's another article: http://www.gamasutra.com/view/feature/1735/the_ten_most_important_video_game_.php

Patents are controversial in games -- it's generally very bad press to be caught trying to shut down your competitors with lawsuits.

off topic --
I read over Creative Labs patent on "Carmack's reverse" recently, and IANAL, but I found that it's claims were very narrow and easily avoided. e.g. by changing the direction of your z-test, or the order of rendering, you can still do "Carmack's reverse"-style "z-fail" stencil shadows, but in a way that's not covered by the patent's claims.

My favourite game patent is that sega owns the patent of having a floating arrow in a driving game. Which the created as part of a forgettable late 90's game called crazy taxi and from what I've read they have rigorously enforced their ownership of this patent. So next you play a driving game and wished there was a floating arrow pointing you in the right direction you can blame sega.

Which is also the problem with game patents in that developers and designers are more than capable of finding alternatives solutions rather then paying to licence the patent.