The new FTC guidelines went into place at the beginning of the month, so if you're posting sponsored reviews, even if your payment is nothing more than a free sample of the item, you have to disclose it on your blog. I wrote a boring article about how it works and what you're supposed to do to comply with the new guidelines.
Basically, if you're giving a sponsored review, it's an advertisement. It's not about journalism or media law or what rights bloggers have or any of the rest of that. It's about complying with the laws that every other advertiser has had to comply with for decades. It's an ad. Disclose it. It's not the end of the world, like a lot of bloggers have decided. It's long, long overdue, in my opinion.