From athis Security Focus Article.
“Dave had some surprises up his sleeve as well. You’ll remember that I said he was using a ThinkPad (running Windows!). I asked him about that, and he told us that many of the computer security folks back at FBI HQ use Macs running OS X, since those machines can do just about anything: run software for Mac, Unix, or Windows, using either a GUI or the command line. And they’re secure out of the box. In the field, however, they don’t have as much money to spend, so they have to stretch their dollars by buying WinTel-based hardware. Are you listening, Apple? The FBI wants to buy your stuff. Talk to them!
Dave also had a great quotation for us: “If you’re a bad guy and you want to frustrate law enforcement, use a Mac.” Basically, police and government agencies know what to do with seized Windows machines. They can recover whatever information they want, with tools that they’ve used countless times. The same holds true, but to a lesser degree, for Unix-based machines. But Macs evidently stymie most law enforcement personnel. They just don’t know how to recover data on them. So what do they do? By and large, law enforcement personnel in American end up sending impounded Macs needing data recovery to the acknowledged North American Mac experts: the Royal Canadian Mounted Police. Evidently the Mounties have built up a knowledge and technique for Mac forensics that is second to none.”