Because I could never say it better than Tim, here is his explanation (and pictures) on FTC disclosure:
Beginning December 1, 2009, the FTC requires bloggers to provide disclosures whenever there could be hidden interests or unspoken biases related to recommendations.
Per the FTC rules, if I interview someone and they grab the bill for lunch, I would need to specify this. Ditto if I use an Amazon link that gets me 8 cents instead of an Amazon link that gets me 0 cents. If someone gives me a comfy t-shirt with a logo and I wear it in a photo, same deal. Disclaimers all over the place.
This would be tedious for me and a continual eye sore for readers. But rules is rules.
To cover my ass and preserve your reading experience, please assume that, for every recommendation, link, and product I use, the following all hold true: