Groupon is moving from the once-lucrative model of daily deals into more direct e-commerce sales, bringing it into competition with powerhouses Amazon ( AMZN) and, to a lesser extent, eBay ( EBAY).

FORBES: Groupon: A Train Wreck in Public Sight

It is true that the combined firm would dominate the markets for instant messaging and web-based e-mail, but neither is lucrative.

ECONOMIST: Microsoft, Yahoo! and Google

It is the latest US e-commerce success to eye the lucrative European market, following on the successful launch of online retailer Amazon.

BBC: Priceline plunges on competition fears