Maintain a list of frequently-suggested suggestions
Short, concise description of the idea
Place a link somewhere prominent (on /suggestions/ or on the community page) to a list of suggestions that are re-suggested a lot.
Full description of the idea
This idea is based on the comment here by tribelessnomad.
The idea would be to maintain a list of suggestions that are re-suggested again and again and some mechanism of directing people to it before they post a suggestion.
An ordered list of benefits
Reduces potential frustration of the poster when they are told that their suggestion has already been posted a million times.
Reduces frustration for regular readers of suggestions.
A useful resource to refer people to.
An ordered list of problems/issues involved
Adds another possible step that people should go through before posting, and having a lot of steps might annoy people or make them less likely to do any of them.
Requires more maintenance.
Might not be that useful because of the difficulty of tracking the frequency with which suggestions are posted (though I think the regular readers could come up with some).
An organized list, or a few short paragraphs detailing suggestions for implementation
Make a new category in the memories called "Frequently Suggested" and provide a link directly to it from the community page.
Suggestions appearing in this category would also appear in their normal categories.
(or) maintain a separate page with a summary of each suggestion that's frequently suggested (probably no more than ten or fifteen) and what its status is (unworkable, workable but not being worked on, being worked on, stuff like that).