Napster (NSDQ: NAPS) subscribers using the service after Feb. 17 will be giving the gift of data to Best Buy. In an “important announcement” sent to subscribers this morning, Napster warns that its October 2008 acquisition by the retailer means “any personal or other data that you share, or have shared, with Napster may also be shared with Best Buy and/or its affiliated companies.” Napster and Best Buy, which paid $121 million for the music service, promise to abide by privacy policies but the message doesn’t spell out how the data might be used by Best Buy or its affiliates, which could include the UK’s Carphone Warehouse. Using the account after Feb. 17 means you’ve agreed to the change, so anyone who wants to avoid the conflation of information needs to cancel by then. I’ll be doing just that.