At the risk of sounding old and out of touch (which couldn't be further from the truth, of course), I'd only just started to get my head around the various debates about whether or not downloading music (legal or even illegal) might be a good or a bad thing for the industry - and now the debate has already moved onto the ethics and merits (or otherwise) of streaming.
As someone who can confess to having never used Spotify and who frankly feels uncomfortable at the notion that the whole concept of owning music is redundant, I'm nevertheless interested to hear the arguments advanced on both sides. On the one hand, streaming would seem to provide valuable exposure for up-and-coming artists who can use it as a promotional tool. On the other, however, the low rates paid by legal streaming services like Spotify mean that many artists don't feel they're fairly compensated for their efforts and that some faceless suits are instead making money at their expense.
Of course, the response to that might be (a) it was always thus, regardless of the business and delivery model (record companies have been screwing over bands for their own personal gain since time immemorial) and (b) if this helps prevent cynical careerists trying their hand at music-making simply because it's perceived as lucrative, then all the better. And yet the industry can't survive if circumstances dictate that artists are unable to pursue a dream and attempt to realise their visions. Man can live on bread alone, though man does at very least need bread.
Anyway, here's a handy survey or articles and links on the subject which might help you to make up your own mind.
(Thanks to Simon for the link.)