There's long been a defense - moral, if not legal - of people sharing music on peer-to-peer networks on the basis that they're probably the sort of people who buy more music than average anyway. Sure, it might be soft-stealing, but it's still your best customers.
Now, a survey has confirmed that to be true - at least in Canada. The Impact of Music Downloads and P2P File-Sharing on the Purchase of Music: A Study for Industry Canada has studied 2,100 Canadians and concludes:
It's important to note that they don't find filesharing increases CD sales as an absolute, but filesharing appears to make filesharers more likely to buy more music.
In effect, it's something the labels should at least see as a positive good, if not actively encourage. Based on this survey, anyway. And anecdotal evidence. And common sense.