I believe the difference is that by the time you're facing a breathalyzer--which as you point out, there are penalties for refusing--you've committed some sort of violation. At that point, you're interacting with the police and if they have reason to believe you are under the influence--either due to the previously cited violation or via observable signs (smell of alcohol, slurring of words, etc.)--they can begin the series of tests to confirm their suspicions.

In this case, you're just pulled over and and checked for no valid reason other than everyone is being checked.

Is now when we drag out the "If you haven't done anything wrong, what do you have to worry about" line?

At my previous company, we went the other direction...no personal equipment was allowed. If you needed a tool (e.g. a laptop), it was provided.

We didn't want the liability of damage or theft of someone's personal equipment. Further, we didn't want to deal with things like users bringing in tools that impact the network, we didn't want to have any issues with software licensing (who provides or you bring in non-licensed software), etc. We also had problems with people bringing in things like printers and then having the company pay for ink (that gets expensive) or wireless routers and creating new and unauthorized access points. Beyond even things like people wanting to bring in their own [monitor, video card, sound card, speakers, desktop, etc], we unfortunately faced the issue of dealing with these things (prior to the policy) when on rare occasions someone was fired and IT had to dismantle a PC, etc.

I guess I'm a fan of keeping work and personal apart.

Even better, here's someone who has already built data centers in silos: http://prairiebunkers.com/