Maybe it's more accurate to say 'the people who easily fell for Groupon's sales people'. In my area the various daily deal sites have very aggressive sales fleets, who literally go door to door in shopping streets convincing owners to put up a deal. Many of them lose money or barely break even; but then again some of them owe it to themselves (I bought a deal once and went back afterwards; she then said 'I'll give you the same price you paid for the groupon, because other customers have complained that they didn't think it was fair they had to pay more when they came back' Wtf?)

Anyway, I don't have exact data of course, but I've been interested in the business model for years, so I tried to get as much information from business owners as I could every time I bought a deal. The overall picture I got even after a few years (so since 2010-2011 maybe?) was that the typical groupon customer had distilled to the cheapskate vendor-hopping type (before that, when groupon was the hot new thing, it was mostly early adopters who weren't really price sensitive, but for whom getting a 'deal' was more about the social validation aspect of looking like a savvy consumer).