netmeg - 3:25 pm on Aug 29, 2012 (gmt 0)
You could load it last with CSS I suppose - just put it at the end of the page, but use CSS to float it back up where it's supposed to be.
Everything Google (and even more, FB) seems to slow down a page. I notice some days where the ads seem to be really zippy, and other days when they load like dogs.
Running a tool like the pingdom loadtime checker can point you to what elements of a page are slowing it down the most.