BEWARE: Creates Strange Ads on Google Rated 2 out of 5 stars
I just spent the last two hours scanning, removing programs, doing anything I can think of, and then finally removing add-ons one by one and guess what? Diigo's add-on is the one causing my red alert virus panic! Their latest version (18.104.22.168) places ads at the top of my Google search results. They look just like Google Ads(!!) but all the ad links start with "http://62972.xml.premiumxml.com/..." as opposed to "http://google.com" which is usually appended to Google Ads. I probably wouldn't have noticed except that I have AD BLOCK and I shouldn't even be seeing ads unless I whitelist them. Plus, there's no way to even tell that Diigo is connected unless, of course, you start disabling each add-on one by one to see what happens. This is really infuriating! I've been using their service everyday since I transitioned from Delicious but apparently they're not very trustworthy.
[Note]: It looks like Diigo may have reverted their add-on back to the prior version of 22.214.171.124 or at least that's the version currently listed on their add-on page. The one that adds 'incognito' ads was the latest update, 126.96.36.199. However, the add-on doesn't automatically 'down-grade' to the prior version and I haven't received or seen any official notice regarding their spamware addition so they might be trying to slip this under the radar.