So SaaS is cheaper than installing your own software, right? Don't count on it. "If you go into a SaaS agreement believing it's going to be less expensive under all circumstances, you should reorient your thinking," says Rob DeSisto, an analyst at Gartner Inc. There are all kinds of extraneous expenses that SaaS customers need to be aware of, according to DeSisto. Those include setup costs, training fees, storage limits and the costs of integrating with other applications.

Here are the top 10 gotchas in SaaS agreements that corporate customers should watch out for:

1. "I agree" to what? SaaS providers typically send electronic contract notifications to customers with an "I agree" button for them to click, says Pat Cicala, president and CEO of Cicala & Associates LLC, a consulting firm in Hoboken, N.J. "People usually get sick of reading these agreements online and end up clicking 'I agree,'" says Cicala.

IT organizations that are poorly governed or don't have a centralized Web licensing strategy run a significant risk of having business leaders agreeing to software terms they're not familiar with. "You've got business buyers making a lot of the contractual decisions, and they're not savvy in a lot of the contractual issues," says DeSisto. For instance, most business leaders don't know enough to ask if the vendor's data center is staffed by people with proper security certifications or if the vendor is ready to comply with the SAS 70 auditing standard.

2. Easy installment plans. For customers, one attractive characteristic of SaaS agreements is that they don't require a huge upfront financial commitment to start a service. But even though there are advantages to paying for the service on a monthly or quarterly basis, few customers realize that they can pare their yearly costs by 5 percent to 15 percent if they pay for an annual SaaS agreement all at once, says Michael Mankowski, senior vice president of Tier 1 Research in Minneapolis.