ICloud – Is it possible to initiate “delete from iCloud” from iPhone

According to this support article from Apple, you have to delete it from your iTunes library and then it will prompt you to delete it from iCloud/iTunes Match as well. I don't know yet if there's a way to delete it from iCloud while keeping it in your iTunes library.

It does appear, if you follow these instructions, that it does automatically disappear from any iOS device set up with the same iTunes Match account.

It's been confirmed elsewhere that metadata alone will not give success in matching (if it were, someone would quickly find a way to just create thousands of dummy files with the right metadata). Some audio fingerprinting is going on, and you can test it by changing the metadata of one track to that of another one, and see if if matches the audio or the metadata. Still, metadata plays a role as well.

MacWorld have a note on the problem of one or a few songs not matching from an album: Basically, it seem to affect specific songs (rather than just randomly failing every n:th song). Two possible reasons for this:

1. The audio or metadata specific to that track confuses the matching algorithm (as we know, audio fingerprinting is not an exact science)
2. There is a rights issue with particular tracks that Apple haven't been able to find agreement for.