Well, it gives careless users more rope to hang themselves, but I'm not sure it changes anything in principle. The Linux version at least works by running a binary that they ship you, which runs with your uid and communicates with their servers. Short of building from source yourself (if you can get the source!), you already have to trust them to ship code which looks at only the stuff that they're supposed to be looking at, and not to be rifling through your firefox history on the side.