There's an assumption that it's mostly small and midmarket companies that are interested in cloud computing, since they don't already have huge IT infrastructures, while large companies want to keep everything inside their own firewalled data centers. But new research from Forrester indicates that conventional wisdom is wrong.About one out of four large companies (1,000+ employees) surveyed by Forrester plan to tap an external provider soon, or have already tapped one, for pay-per-use computing of virtual servers, which Forrester calls infrastructure-as-a-service. By comparison, just 18% of midmarket and 15% of small businesses have plans for IaaS. Those figures come from a survey of more than 2,600 "hardware decision-makers" at companies.

Another misconception: Large companies are more interested in building "internal clouds"; in other words, their IT departments offer pay-per-use computing within their own companies. Forrester's study found that 33% of large companies plan to use a service provider for IaaS, while just 24% want to run their own clouds. Forty-four percent plan to use a mix of both.

And the larger the company, the greater the awareness of cloud computing. When asked about their "level of awareness/interest" in pay-per-use computing, such as Amazon's EC2, Savvis, and Mosso, 27% of respondents with more than 20,000 employees say they are using or planning for it; 23% say they're interested but don't have the budget for it; and 28% aren't interested. Twenty-one percent of respondents at very large companies have been living on a desert island: they said they're not aware of this thing called cloud computing, or they checked the "don't know" box.

Companies with 5,000 to 19,000 employees fared worse on awareness, with 23% saying they didn't know or weren't aware of pay-per-use hosted, virtual servers. Slightly more than one-third knew but weren't interested, while 21% didn't have the budget for it. Twenty-one percent were planning or already using it.

Companies in the 500 to 5,000 employee range were slightly more with-it than their big brothers, with just under 20% saying they didn't know about cloud computing. Unfamiliarity was much higher among small companies: 26% of those with 100 to 499 employees didn't know about it, and 31% with those fewer than 100 employees weren't aware.

This research, published in a May 29 report by analyst Frank Gillett, tells us that most large companies are paying attention to this sometimes-hazy concept called cloud computing, and a sizeable minority is jumping into the cloud.