Patent trolls buy them and keep them to use them eventually, but will wait a long time before doing so so that lots of members of industry will have infringed b

Patent trolls buy them and keep them to use them eventually, but will wait a long time before doing so so that lots of members of industry will have infringed before starting to sue. In trademark law, you can't do that: if you're lax and let your mark become generic, it's basically impossible to go back and go after infringers after the fact (this happened to "nylon," for example). There would still certainly be patent trolls, but as a start-up, you wouldn't have to worry as much about them... if you wanted to implement a feature that other companies were also implementing, you could do so with a reasonable amount of safety: either they weren't patented, or they were and there would be noisy lawsuits going on about them, or the patents existed but were no longer valid due to lack of defense.