* Sometimes, issues are just questions that belong on StackOverflow or any other forum online.
* Often people suggest pull requests that don't really fit what you see as the roadmap for the project, you have to be polite and respectful.
* There's the case of beginners trying to jump in, if your project is something that appeals to beginners (eg:Rails), you are in for a whole bunch of other issues supporting the getting-started.
* There's a lot of stress involved with managing all of this, if you are alone in the project it can get pretty overwhelming.
* Finding collaborators on open source projects is not easy as well, most of the times the project README doesn't suggest that collaborators are welcome and appreciated.
* Forking creates a lot of fragmentation.
* I can think of many projects that lost the steam. Resque is the perfect example for me, even with new contributors it failed to get going and Sidekiq won.
* We still need to figure out a reward system for open source to prevent maintainers from losing steam along the way.