I run a price comparison site. I noticed recently that for one dealer in particular, if I open his product page in 2 browsers, side-by-side--one normal view, and the other through the eyes of my web-crawling script--the prices my web-crawler see are 3% lower across the board, making this dealer the cheapest in my pricing tables.
It really seems like they're using cloaking to be #1 on my list, but I want to give them the benefit of the doubt. I know I'm not viewing cached pages, because the values on the "fake" pages update constantly along with the real pages. Is there anything else I can check to know for sure that they are or aren't cheating? I'm a n00b at this black hat stuff, so I really don't know what to look for.