Who are the five most notorious Presidents in American history?

Depends on how we decide to measure worst... ethics, respect for law, human rights record, prosperity of country. It's not likely that the metrics used to determine most notorious are going to be the same... for many Iran-Contra wasn't a big deal, for others it was huge. For many Clinton's and Kennedy's infidelities were a huge deal, others simply don't care. President Andrew Jackson was probably one of the worst by anyone's standard. A better President than Buchanan might have prevented the war between the States from ever happening. From my perspective George H. W. Bush was perhaps the best President we have had during my lifetime and that his son was the worst.

I think it's interesting that they made absolutely no mention of Jackson's role in forcing the treaty that resulted in the trail of tears. The man was a monster.

Easy one...
1. Obama
2. Wilson
3. Grant
4. Clinton (extracurricular activities gets him in the Top 5)
5. Tie....Roosevelt in his 3rd term / Nixon and Watergate

Notorious... No particular order.

Nixon, tricky dick.
LBJ, well.. ups and downs but had a fairly negative political view on black voters.
Andrew Johnson, he hindered reconstruction of the South.
Pierce, joined the Confederacy nuff said.
Buchanan, he didn't prevent the expansion of slavery or stop the war from happening but on an interesting side note apparently he bought slaves and freed them.