Did you search for Lensbaby on google recently? It could be that. These sites (google, facebook etc.) are tracking every site you visit and will display ads accordingly. Not sure if that's true in your case as well. You can use some plug-ins on chrome to block these sites from tracking the sites you visit.
Lensbaby isn't a targeted ad; it's not dependent on your google searches. Maybe one of the mods wants to chime in, but going to Mu-43.com - Micro Four Thirds News and Rumors (the front page) in a browser on my desktop, on the left side is a Lensbaby ad, a targeted ad (for me it's an IR ad, I can tell this one is dependent on my cookies/search history), and then a B&H ad. Lensbaby and B&H seem to be sponsoring this site and are getting non-search-dependent ad space. That the icon got replaced is probably just a glitch with the app, or are you using Safari?
Yup, I also see... Lensbaby, Advertisement (targeted ad), B&H Photo... But they are off on the side and not over anything else. The "Advertisement" section is blank for me. xD
I don't see them on this site, but on the Serious Compacts sister site, I see it and it is under that says "sponsors". I assume they are advertising. Someone has to pay for the site to exist.