As noted, our team developed software solution platform that powers many Groupon and Fiverr like sites.
Initially, the development wasn't much interesting as now; there was less freedom to add our own idea--as customers would be asking exact or similar features of popular site. Taking GroupDeal, when we added merchant interface, many customers didn't want it as it wasn't a feature available in Groupon and LivingSocial; but Groupon has come up with similar feature as Groupon 2.0! We've even added friends mod as I have a gut feeling that Groupon will definitely take that direction. From the very beginning, we predicted that Groupon is good idea out of Woot, but the interface isn't good--something like Digg would be ideal for Groupon; but, we couldn't do anything here. Also, the initial FUD was that our software didn't scale on load--even when we shown it's scalable than Groupon; and that got settled down once MySuperDealToday could sell 1,440 deals in a day
And, when we added PayPal adaptive payment and PayPal preauth option (also, we referred it as "PayPal connect"; I'm quite surprised why PayPal isn't even trying to popularize it?) to FPPlatform, it wasn't much interesting to customers.
There are lot of ideas and possibilities for folks at PayPal, Google, delicious, Yahoo!, Groupon, Fiverr and any other internet companies; but it all looks like they don't have enough freedom like many of us in IT solutions industry.