Nano - 10:35 pm on Apr 16, 2011 (gmt 0) [edited by: Nano at 10:38 pm (utc) on Apr 16, 2011]
I'd also like to note that the in-text links Technorati uses are not marked as ads but are probably considered ads.
Plus, the text-link ads on technorati's pages are not nofollow links.
Most of the contextual ad programs are nofollow, and say advertisement somewhere. You've seen the ones with the pop-up window, they mark advertisement there.
[edited by: Nano at 10:38 pm (utc) on Apr 16, 2011]