A few points

Security through obscurity. There are very few known exploits for Linux period. The Maemo tablet is an Arm processor based device running a generally very secure operating system.

Services: The tablets in the hands of "amateurs" is just an email / web client. Any decent IT dept should have those services appropriately locked down.

Geek factor: Those smart enough to do more with their tablets are generally smart enough to avoid problems.

Right now I'm violating official company policy as I type this at work on my MacBook pro. But I have a gentleman's agreement with IT. They cut me some slack and look the other way on my setup and I help them with some of their tasks in my work area.

It really boils down to platform doesn't it? AFAIK, There's never been a cross platform virus and there's only been one self replicating linux virus in the wild.

The reason IT security is so paranoid is thanks to Windows success, there is not enough diversity in the platform gene pool. If there were a variety of platforms and operating systems deployed, the entire IT ecosystem would be more exploit resistance. We're all windows in-bred here so we are all vulnerable to the same exploits.