Dion Hinchcliffe has put together a draft list of the first-order elements of Web 2.0 thinking. Number five (of sixteen):

Be prepared to share everything with enthusiasm. Share everything possible, every piece of data you have, every service you offer. Encourage unintended uses, bend overbackward to contribute, don’t keep anything private that doesn’t absolutely have to be. Go beyond sharing and make discovery, navigation easy, obvious, and straightforward. Why: In return, you will benefit many times over from the sharing of others. Note: This is not a license to violate copyright laws, you will not be able to share your ripped DVDs or commercial music recordings, those are things you agreed you can’t share. But you might find yourself using and sharing a lot more open source media. And for heaven’s sake, learn the Creative Commons license.

Great advice, but make that Creative Commons licenses. The rest of the list well worth reading too.