I think it's a bit disingenuous to compare yourself to Spotify (at least on HN). I think a big part of Spotify's business is that they have agreements with the big 4 record companies for each country, and they're rolling out their service as they get the deals signed in each country. So if I use Spotify, I'm listening to music legally, and a lot of music is available.

You are using Youtube, so you're limited by what's on Youtube, and various other strings attached.

Anyway, I think the site is a lot of fun, rock on! =)