I've been a big user of deal sites because I love shopping and bargains. No more though. There seem to be a few good players, but there are some roques out there too.
I've had a few complaints with some sites, and most were handled well. The worst ever experience I had was with voucher.com.au. Battled to get my money back, and ended up joining many people complaining to Fair Trading. See what I mean, Google "voucher.com.au complaints".
As with all trends, the strong and smart will rationalise and prosper in the daily deals market, and the weak will be gobbled up or just vanish.