Amnesia is and always has been that bitch. A classic.
In my fantasy world, the original
Circus campaign would have lasted around a year with a typical singles run, then they'd re-release the album (as was all the rage back then) around its first anniversary in November/December 2009 with
Amnesia as the lead single - it's got a bit of a Christmassy feel so is absolutely perfect for that time of year. (
3 could have gone on that re-release too, and been the second single from it.)
Anyway,
Amnesia blows up, gets played everywhere you go and storms the charts worldwide just like
Womanizer did a year earlier, the album gets a strong second wind (especially with a follow-up like
3), and all is great in the world.