This is a relatively minor UI annoyance. On the main page (https://stackoverflow.com/), the block of Favorite Tags are immediately below the Ask Question button and above the careers ad:
but on the questions page the careers ad is above the favorite tags:
The different positions is only a minor UI annoyance, but there's often some delay in loading the careers ad, which means that the favorite tags jump down when the careers ad appears. If the browser is sluggish, it's not uncommon that I click on a favorite tag only to end up on the careers page (because the careers ad is loaded by the time the click is processed), and this is a bigger annoyance.
Is there a reason for the difference, and if there's not some compelling reason to have the careers ad above the favorites tags, could the favorites tags always be placed above?
As of Sep. 17, 2013, it appears that things have shifted around a bit, with the main page looking like this (notably, with no careers ad):
and the questions page looking like this (with the careers ad):