Along with a disabled spot actually causing the problems that it was supposed to prevent we have various studies that show that the more safety devices one employs the more risky his behavior becomes. A recent bike helmut study comes to mind but I'm too lazy to look it up. Does anyone suppose that just because we have a SPOT or SAT phone that we might do something we ordinarily would not. Personally, I have backed off of a few bushwhacks when solo simply because I had no means of initiating a rescue if I became lost or hurt.
There is anecdotal evidence from rescue personnal that outdoor people are generally engaging in more risky behavior because of the spread of rescue communication devices.