I still buy CDs and love doing so - I think it's awesome to have them, but I think the because an issues with having a lot of variety and a big taste in music, it'd very very expensive to buy
all of the CD's (and still pay for live shows too), whilst many use that as a defense for acquiring illegal copies, but before stuff like Spotify I went without, or listened to samples or watched their videos (or listened to Last.fm). But services like Grooveshark and Spotify provides you music for free or via subscription and it has lead me to buy albums I've enjoyed. EG. I got into Sigur Ros because of Spotify, now I have one of their albums and listen to that instead of hearing it on Spotify.
I'd agree it's no replacement for 'owning' the CD. As far as I understand, it's up to the record companies to distribute the music of their artists and offer them a fair percentage of sales. My
assumption (and you're welcome to correct it) and to me it's the logical answer, it is that bands would get money based on how many people use the services to listen to their music, I assume it'd be similar to PPL licensing or similar radio licenses. The money can be based off of advertising, like with commercial radio. Some Student Radio, like ours, was paid for by the Students' Union, and as far BBC radio, I assume they take a chunk our of the TV license most Brits pay for. I'd probably equate it closer to that than to that of music piracy.
I don't think there's an issue with ethics, so long as contracts are being fulfilled (thus no laws broken), no agreements broken, the fans are happy and the record companies pay their artists for their hard work.
Services like Spotify hold agreements with record labels and record labels hold agreements with artists. It's one reason why Spotify is not able to have an agreement with every record label, nor every artists nor every album. E.G. There's a lot of Iced Earth albums I can't find on Spotify, I can listen to their newer stuff, but not their older stuff, on Grooveshark, it's actually the opposite, loads of old stuff, but not much of the new stuff. I would assume they were produced by different record labels and they have different agreements.