However, the point in the OP about Camera+ seems a bit more legit. Rejecting an app for doing X and then doing X yourself in the next release seems like a huge double-standard, and where there are double standards there is foothold for allegations of anti-competitive behavior.

That said, however, the difference between me (sitting in a cubicle typing this) and the creative forces behind Instapaper and Camera+ is (hopefully) that where I see small developers being turned into digital sharecroppers by a dictatorial corporation, they see an opportunity to differentiate themselves from the stock offering by excelling in the very specific area they're focusing on.