It doesn't happen very often but yesterday I came across a pretty cool MPU while browsing the Internet (So not from a link or a blog about advertising ;). It's an ad I spotted on College Humor, (While showing this video to someone; it's really good check it out) so it's probably still playing on some pages if you want to try it out - refresh to cycle through the ads served.
I haven't checked yet but I imagine most certainly this is CP+B at work here for Burker King who as far as I know about created the first augmented reality feature in an online ad. And while you could argue how useful it is; what's most interesting is that the symbol used for the AR to display is something most people [in the USA] would have in their pocket: a $1 bill.
Now whether anyone outside of complete geekiness and/or who works in advertising would wait and play with the AR and go shuffle in his pockets to find a $1 bill is also arguable, but you don't need many people to start showing others how neat this little feature is (I'm also guessing you need a good bandwidth)