I would like to see these questions as on-topic here. Story identification questions are popular on SciFi, and I think song/artist identification questions could become popular here.
I don't necessarily think that they will be hard to find in the future for those with the same question. Sure, if someone just posts a sound file and says "What is this?", it doesn't have much usefulness outside the Original Poster. However, I think that most questions will offer more information than that.
For example, they might ask something like this:
What is the name of the classical music in “Anger Management trailer”?*
Or maybe something like, "Who sings the song from the Oreo commercial 'Wonderfilled'?" **
With something like this, there is enough text about where the music is found that it is searchable.
Questions about classifying artists and songs into genres should also be on-topic, in my opinion.
I know that on Music.SE, we often get off-topic questions about identifying songs like this. It would be nice for that type of question to have a home on MusicFans.SE, and I would enjoy answering some of those.
* In my defense, I was relatively new to Music.SE at the time I answered that, and I didn't know that those types of questions were off-topic there. I refrained from answering those types of questions in the future. :)
** This one is easy to Google, but you get the idea.