Don't worry, this isn't another topic about redemption rates!

Has anyone else made bad decisions in collecting miles that turned out to be very poor value?

I've realised that I still have a Blockbuster DVD subscription that I had forgotten about so the 500 mile sign-up bonus has cost about £60 and I only ever watched two DVDs using the service.

I'm not really sure why I signed up in the first place because I already use Lovefilm and don't really use miles anyway.