For those who go straight-to-comments on HN (myself included):

Users first play a series of games with cartoon spiders, which start out as cute and harmless-looking but gradually become more realistic. One early task involves helping a spider hide in a slipper while someone is using a vacuum cleaner.

You're also missing a spider in a top hat.

NICE (the UK "death panel") has guidance for computerised CBT. It's interesting reading.

It's surprising how effective a short bit of work can be to overcome quite deeply entrenched phobias.

http://www.nice.org.uk/guidance/TA97