Amazon investors might have finally heard the news they have been waiting for: The retailer is raising shipping fees. Amazon has 237 million active customers but as a general rule makes almost no profit. Thursday's announcement that the company was considering raising prices by as much as 50 percent on its $79 Prime shipping program could mean $500 million for its skimpy bottom line. The news came in a conference call when the Seattle-based retailer discussed its fourth-quarter earnings. The announcement helped deflect disappointment that Amazon's torrid growth might be slowing. Amazon has been pouring money into new ventures, ranging from new warehouses to free videos for Prime subscribers. The eternal question is when it will turn all that expansion into profit.

Raising fees for the estimated 25 million Prime subscribers indicates that moment might be sooner, rather than later. Still, there are risks for Amazon. "The more expensive Prime is, the more they are going to have to live up to their promises," said Sucharita Mulpuru, an analyst with Forrester Research. "In my experience, a significant portion of the deliveries take more than the advertised two days." By her estimates, Amazon is losing $1 billion to $2 billion a year on Prime.