I get e-mail alerts from different Groupon sites but have only purchased two: one for a dinner date with hubs at Barbara's (which we have yet to enjoy) and one for massage (somewhere in Makati). I feel both are good deals. I'm not sure if these sites are offering phone alerts like SharisBerries Twitter is doing for their promo codes but since a lot of people can access their mails through their phones, I guess these deals are now really that accessible.
However, it seems some Groupon sites are actually being deceitful and misleading. They say you're getting a 50% discount when they're really offering the deal at its original price. Or, it's really a 50% discount if you're getting the service fom a higher-end provider, but the deal's actual original price from the adverising company is way lower. And, in the case of some, travel agencies are giving the same deals or restaurants are actually just throwing in free iced tea :)
So, before you buy... contact the company first or do some research first as to how much the goods really cost. See if you're really going to save money on it before committing your pockets to it. There could be better deals out there.