[Woost]

Groupon's business is basically all sales and marketing. The v1 tech behind the deal-a-day offerings is trivial. (leaving aside recommendations and such)

You need to be very good at signing up businesses and getting good terms for your company to succeed. In addition, you need to figure out how to get a stable base of customers of your site.

Basically, Groupon clones have very low technical barriers to entry, but if you don't have a really good sales and marketing staff you're in trouble.