A recent FTC ruling actually made "paid" endorsements without disclosure illegal. TechCrunch could be hit with considerable fines if they didn't take action on this.

Relevant excerpt: "The revised Guides specify that while decisions will be reached on a case-by-case basis, the post of a blogger who receives cash or in-kind payment to review a product is considered an endorsement. Thus, bloggers who make an endorsement must disclose the material connections they share with the seller of the product or service."

http://www.ftc.gov/opa/2009/10/endortest.shtm