"It often comes as a big shock to the infrastructure and operations people [within IT] to find they grossly underestimated the cloud services in use at their organizations," Schreck says. "They realize they have no idea what the application owners [in business units] and developers are up to."

Informal buyers even have their own tech budgets. According to a Q4 2010 Forrester survey 69 percent of 3,000 business managers reserved part of their operations budgets to buy tech services directly, rather than through IT.

A found that 61 percent of business and IT executives said they buy cloud services on the sly because it's simply easier. Half said going through IT takes too long and a quarter said their company's policies forbid them from using the services they want.

That's not necessarily a disaster, but it can set both IT and its parent company up for one, says Susan Cramm, founder of executive career-development and strategy consultancy Valudance. Cramm is also a former CIO of Taco Bell and CFO of a smaller PepsiCo restaurant chain.

Experts say letting managers buy any service they want, when they want leaves the company bleeding money from multiple subscriptions to Salesforce and suffering "cloud sprawl"- too many separate logins, too little integration between instances of the same service and rates that are too high because subscriptions are bought one at a time rather than in bulk.