There’s quite a storm of posts out there right now on how the FTC is taking a look at viral marketing as it is performed online. Overall, it’s a good thing too. But it also means you need to be very careful in what you say about products you recommend on your site if you’re getting anything in return for the recommendation.
If you do any paid blogging or affiliate marketing on your site, a disclosure policy is a generally good idea anyhow. I got one when the whole Pay Per Post storm hit and they realized it made sense.
The most basic thing you need to think about this is that you shouldn’t be making claims you can’t prove. You also need to be upfront about if a particular experience is not the usual. That’s just good marketing even if there aren’t legal consequences to consider.
The big areas of concern are probably areas such as make money online and diet claims, as those are quite prone to exaggerated claims or excessive focus on atypical results. But don’t start exaggerating results in other areas. You could get in trouble anywhere.