If I post a photo of a candy bar on my website, with brand and other text clearly legible, would I be violating any copyright laws?

You’re fine. This would fall under “fair use” – showing a copyrighted product in an editorial context.

If you use the image (and so the name) to promote yourself or your products (such as your site), you can get into trouble. If you just want to show your love of Snickers, you are OK.

If you take the picture yourself, you’re free and clear. If you snarf the picture from a source that explicitly prohibits re-use, you’re opening yourself up to trouble – if the copyright owner notices or actually cares. There is so much image capture on the web that you’d have to really tick someone off for anything to come of it.

Notice Steelmarket’s uninhibited use of the word “snickers” on this website. Same rules apply. There’s no real personal gain on his part… just talking about candy bars using there trademarked name.