May was a fruitful month for e-commerce, as it reached the $12.3 billion mark, up 13 percent from May 2010, according to ComScore.  ChannelAdvisor’s year-over-year same-store sales rose around 84 percent for Amazon and 13 percent for eBay in May, according to last week’s Barclays Capital research note.

Amazon shares climbed 1.4 percent to $186.32 in trading on Friday, while eBay gained 1.2 percent to $28.81.

Not everyone is celebrating the May spending numbers in a carefree fashion.  Some people believe it’s important to proceed with caution as we try to recover from the latest recession.

“We continue to believe the Recession accelerated the Online share shift, and view the possibility of a return to pre-Recession 20%-ish growth rates a distinct possibility,” analyst Mahaney of Citi Investment Research & Analysis said.