Well, actually, the body tag mybloglog wants you to use it after is in header.php.
You'll see something like this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
*bunch of meta tags and gobbledegood code crap here*
<?php wp_head(); ?>
Something like that.... and mybloglog's tracking code goes immediately after
<body> and before anything else that's there like other divs or whatever.
I set mybloglog to load in a client's sidebar on his request, btw, and it didn't work very well at all - I don't know why, but my guess is there's a reason for mybloglog to suggest strongly that you put it where they indicate....