There are a lot of reasons why businesses may be draw to SaaS based applications.   One of them is that they can be a good way for the business to bypass an IT department that they view as being unsupportive or unreceptive to their needs.

IT departments need to be aware of this trend because if not managed it could significantly change the way that IT is delivered to business users, and has the potential to end up costing the business significantly more money.

IT departments need to partner up with the business when it comes to SaaS based offerings.  Instead of seeing them as a threat, they should regard them as just another way they can provide services to their users.   With some services, SaaS will make sense - it will be cheaper, quicker to set up and less costly - but this will not be the case for everything.

That means that members of the IT organization need to be business savvy enough to understand what the business users actually need (which could be different than what they ask for) and help drive the requirements for the applications (and delivery models of those applications) that support those needs.   These needs can also be rationalized over multiple departments to save cost.     To be successful, these people should sit 'with' their business counterparts and form a conduit into the IT department for understanding the changing requirements for business applications.

Without such an approach, business users now have the ability to easily go elsewhere for many of the applications they need.   An IT organization who does not understand what the business needs and is not their partner in creating the right services may find that new services are popping up in every corner of the business, with little oversight, little technical evaluation, and with little consideration for aspects such as security, performance, redundancy, standards and so on.

Business users will likely miss key steps of a SaaS provider evaluation in terms of understanding how resilient their architectures are, what the SLAs for performance and availability there are (and what the fine print really means) and so on.   Ultimately the whole company suffers in this approach.

Better led IT departments will partner up to work with the business and will build the right portfolio of services with the delivery model tied to the requirements of the service.