Originally posted by Rondec I hate to say it, but nikon and canon forums are a big source of this fear. If someone posts a question about Pentax there, invariably, the comment "you don't know if your camera company will be around in five years" comes up. My wife a couple of years ago posted a short entry on her blog as to why she shoots Pentax and several people e mailed her and told her that it wasn't right to turn beginning photographers to a "dying company." These sorts of things get repeated often enough that they sound true, even if they are far from it.
Fair enough, but neither Nikon or Canon users can say for sure that what they have now will still work with what is made in 5 years.
Nikon has been a minefield of lens compatibility since they went AI in the early 80s, and Canon did completely screw their user base once, and would do it again in a heartbeat if they felt the need.
I would ask anyone who trusts Canon or Nikon because they are big to also have 100% faith in Wal-Mart and McDonalds because they are big too.