Think I saw this on the news recently.
If it’s what I’m thinking of the catch is they will be monitoring people’s activity to compile usable statistics for record companies.
I’ll be avoiding it myself as it’s an ad funded product.
The software apparently works by scanning the Gnutella network and filtering out all the crap as well as any files that contain noise or clicks. This means, in theory, that although they may be licensed to offer 25m songs there may be only a fraction of that available.