The UK version has a much worse design:

http://epetitions.direct.gov.uk/departments

Responses are guaranteed after 10k signatures, which is a bit more achievable than the (current) 100k in the US. If they get to 100k then they have to be debated in parliament.

Highest number of signatures is for saving badgers. Which seems very English :)

http://epetitions.direct.gov.uk/petitions/38257

Started by (now Dr) Brian May.