This is a big problem at a lot of data centers. It's very rarely made public. It's bad for business, ya know. I personally know of one incident (at a major data center) where some bad guys stole a bunch of super valuable gear by lowering it out of a window down to street level.

Do you think thieves are more commonly stealing valuable equipment or specific valuable information?

I'd bet money all but a very few are after just the equipment itself.

Step 1) Have your cousin the janitor let you in the back door.

Step 2) Take an expensive looking gadget from the loading dock.

Step 3) eBay it for $10k.

sounds a bit like a shadowrun...