Who would blame them? If you read about some of the latest outages for RIM's service you could think it is not a big deal as most companies have downtime in their IT systems sometimes, that's why nobody claims 100% uptime - 5 nines is agressive. Sure, some systems have maintained 100% uptime for years but that is not the norm, systems fail and more commonly, people fail.
The difference in this case is that RIM's NOC infrastructure is outside of IT's control. Imagine being a CIO for a medium or large company and getting a call Saturday night from the CEO saying his email stopped working as he is headed for an important Golf meeting. You know your email servers are up, you know you have built redundancy into your security systems, and if there was a problem in your server room at least you would be working on it and would have and idea of how and when to solve it. But if the problem is a third party operations center you rely on, what do you tell your CEO? "err....we called RIM and they told us they are working on it...we have to wait."
In that situation, you have no idea what the problem is, or when will it be solved, or if it will repeat itself. Furthermore you have no control - no ability to make investments or introduce safeguards from a problem from happening again. Nor you have an idea of what kind of system exists today to protect you and your critical business information. What are the continuity and contingency plans? As eWeek says "...there seems to be no end in sight." . it is the uncertainity that kills you.
In conversations I have had with IT departments, this comes up often - not only the BES servers are an additional point of failure (and a server with no replication, mirroring or other redundancy/high-availability technology), the NOC is a second one that you can hope/trust will be there to serve your business needs.