• by Wendy Davis , Staff Writer @wendyndavis, November 16, 2007

In preparation for its upcoming reissue of its 1987 album "The Joshua Tree," U2 has released a version of "Wave of Sorrow" -- a track that didn't make the original cut -- on Facebook via the iLike widget.

A video currently is available on iLike's U2 page on Facebook, which currently has more than 1.3 million fans.

This move by Bono marks one more example of how musicians are experimenting with digital distribution.

But it also highlights a potential problem with Facebook's new Social Ads, a platform that attempts to turn consumer "fans" of brands into advocates for them. With the program, users can sign up as fans of particular marketers; when those marketers purchase ads, the fans' photos and names will be included on ads to those members' friends.

One of the many unanswered questions about this program is whether member-fans really are enthusiasts of particular marketers, or whether they identify themselves as fans because they're hoping for some other perk -- such as, for instance, access to music or videos before they're generally released.

Here, it looks like people can stream the new U2 video without formally becoming fans. But that's not to say that other marketers won't offer benefits to people who identify themselves as fans on Facebook. And, leaving aside any legal concerns about using consumers in ads, it raises the entirely separate question of whether the members' endorsement is a meaningful testimonial, or was purchased in exchange for some sort of perk.