Have you noticed that APMEX "buy silver" advertising is popping up just about everywhere? I just saw one of the APMEX ads on a woodworking site: http://www.woodturningonline.com/ . That's pretty amazing, and I think a good thing - creating demand can't hurt prices, and prices going up is good for me...
I believe that some of the advertising you see on the net is based on your web surfing habits. Not sure exactly how it works, but I have read that.
They're targeted ads. You seem them because you go to APMEX and similar sites a lot. Your neighbor who doesn't go to those sites gets different ads.
That is correct. Your surfing habits are being tracked. APMEX has been utilizing this for a long time already. Just dump or manage your cookies and you can nip that in the bud. APMEX also bombards your email account with sales and promos... it's quite obnoxious, 12 days of Christmas was turned into 12 days of inbox e-blast sales gimmicks.