I don't know how many look at the MathOverflow Weekly Newsletter, but these were the "Greatest hits from previous weeks":
"Video lectures of mathematics courses available online for free" from Feb 2011.
"Undergraduate math research" from Nov 2010.
I assume this is an artifact of people editing old, popular posts. It doesn't put the best face on MO. (On the other hand, the "Top new questions this week" do represent MO more accurately.)