Tech investors don't just love hot growth stories, they adore them and will push up multiples to eye-popping levels to have them. That's all well and good so long as the growth holds up, but as these stories transition from growth to execution, the stock returns can fall off sharply.

That leads me to my primary worries about Salesforce.com (NYSE:CRM). There's no arguing that Salesforce.com has built itself into a leading software as a service (SaaS) vendor, and a competitive threat to companies like Oracle (Nasdaq:ORCL), SAP (NYSE:SAP), Microsoft (Nasdaq:MSFT) and IBM (NYSE:IBM). What I do wonder about, though, is whether there's a similar level of intrinsic profitability in the business model and whether the company is generating the real new customer growth that investors are paying so much to get.