The GFDL and CC-BY are rather different licenses. The first is a copyleft license (requires adaptations to be distributed under the same license), the latter is a permissive license (do anything you want so long as you give credit, roughly).

If you don't want copyleft, CC-BY is your choice.

If you do want copyleft, it would make sense to choose between GFDL and CC-BY-SA, which you can think of as the copyleft version of CC-BY. Wikipedia (and other Wikimedia sites) migrated from the GFDL to CC-BY-SA as their primary content license in June, see http://creativecommons.org/weblog/entry/15411

Thanks for not considering a more restrictive license. :)

Which is less important anyway since top100 gives RIAA member companies advertising gratis, even as they persecute filesharing. There's the irony.

Indeed. Filesharing isn't going to break major label hold on our minds any more than sharing copies of Microsoft software was going to break that company's hold on our computers.

Yep, and if we're willing to look to other cultures, it's probably already happening, see http://gondwanaland.com/mlog/2008/02/23/copypop/

TPB is a music (and other media) discovery service to the extent people look at its "top" pages.

Last.fm is of course much more interesting as a music discovery service. For those with concerns like the author of the post, check out http://libre.fm/

Indeed. So obvious, so seldom stated. I made it point 0 of http://www.slideshare.net/mlinksva/five-myths-about-the-future-of-culture-and-the-commons-presentation