I've just had an advert for East Coast as well ....
Anyway, a quick (and basic) explanation about how Google Adsense works for those who don't know.
When you create an ad slot for Google (IE, insert the code into your web page), the Adsense bot scans that page and attempts to place a relevent advert there. For example, a forum about computers and gaming will bring up a lot of adverts from hardware and software companies.
Most adverts are placed on a pay-per-click basis, although some are pay per view (usually 1000 views). If Google can't place a relevent advert, it wil attempt to place a generic advert there instead. Failing that, a public user messege (such as asking for donations to Oxfam) for which the forum will recieve no money from if it's clicked.
Google Adsense does not scan your browsing history in order to match adverts to you, but as I stated, scans the page for relevent keywords in order to match adverts to that particular page.