My experience with successful products is that they get a ton of suggestions which fall into one of two buckets:
1) The suggestion is just plain dumb, either completely unrelated to the project, or showing a gross misunderstanding of the goals of the project.
2) The suggestion is obvious, but very hard to implement.
The reason this is the case is because with a successfully project, all of the obvious and easy suggestions have already been implemented. All that's left are the impossible ones and the ones which don't make sense.
[Here I use "successful" to mean "Enough people use it and work on it that people constantly volunteer suggestions without volunteering patches."]