Salvage these ideas is the key phrase there. We definitely listen and look for trends as far as desired game play is concerned. However, a lot of times criticism or suggestions on the forums are not made in a way we can take them. Example, "Sonic Generations sucks!" is not a suggestion! However, "Hey, I didn't like that in Sonic Generations ______ happened when you pushed ____ button" or something similar is something we can listen to and pass along.
As far as content ideas, as Clumsy and Ruby have said before, we can't actually accept any fan content ideas for legal reasons.
And Treacher brings up a very good point and another one that is difficult to work around - most of the time you guys aren't privy to what games are actually in development or what games are a silly rumor. Sometimes when you guys see demos or previews for a game, the game is too far into production to add things in. Sometimes people make suggestions that are very good suggestions but they don't understand the process of building a game or what it would entail to incorporate. Sometimes it just might be something that they don't want to include.
From what I understand (since I haven't been with SEGA for too terribly long), NiGHTS as an NPC in Racing was a result of community support of NiGHTS - he wasn't originally anywhere in the game. I believe that Tails being added as a playable character for Sonic CD was also a result of the community's affection for the little guy. Bottom line: If we're hearing a consistent want/need from the community, the Sonic Team definitely hears it.
I don't know if this means anything significant, but I figured if we posted our criticisms and ideas in a well thought out and respectful manner, maybe Sega will take note and consider the content given.
I dunno, it seems like something is better than nothing.