To be or not to be - smart?

Had an experience this morning that has me seriously questioning myself. I took a kid I don't know from Adam to school out of sheer pity for him that he missed the bus.
I didn't actually see him miss the bus, but he was wearing a backpack and walking in the school's general direction, coming from the bus stop just down the street from our house.
Why is that a big deal?
Because I am someone who takes security measures to a degree that could definitely be classified as over-the-top and/or paranoid.

For example:

You know all those email fwds about precautions women should take? Not only do I read and save every one, I take notes. And you know the ones describing specific attacks? I immediately "snopes" it for validity and then I check the local crime activity.

I'm constantly on watchdog.org looking for any new sex offenders in the neighborhood and reviewing ones I already know about. (I used to print out their pictures and keep it by the door)

I don't use my mailbox for outgoing mail because I don't want anyone (including the postman) to see what kind of correspondence I keep.

I always keep my doors locked during the day and WILL NOT open the door to anyone I don't know and/or am not expecting. I don't care if it is just a kid.

And if it's a cop, I write his badge number down and then call the police station to confirm why he's there.

I drive different routes to drop off / pick up my kids from school just to "throw off" anyone who might be watching my daily routine.

After shopping w/ my kids and I reach my car still using a shopping cart, I refuse to take the time to return it if the kids are already in the car. (Okay, I know that's not such a biggie, but I do have guilt over it.)

I always cover the number pad with my free hand while keying in my PIN number at gas stations. Always.

If I ever do have to enter the store at the gas station (which I try very hard to avoid), I always first analyze the cars parked out in front. If there's ever a big van I won't go in.

I never eat with my back to a window or a door.

Blinds must be shut at night in the "up" direction, because you can actually see inside a bit if they're shut "downwards."

All windows must be covered at night. Period. No exceptions. And if I'm at someone else's house and it's not done, I'll do it for them.

I am the world's fastest ATM user. And I always make sure to look right in the camera so if something should happen at least they know it's me.

I won't talk on a cell phone while walking around. I must always be alert and aware of my surroundings.

I will not give out any account info over the phone to anyone unless I'm the one who initiated the call. Seriously. If they call me for whatever reason, I ask for their number so I can hang up and then call them back.

If, at the park or the store or wherever, someone makes a comment to me about my kid for seemingly no reason, I give them a suspicious look and then leave.

I am always suspicious at parks of men with no kids or dogs.

I am continually "checking my memory" of random license plate numbers to see if I could recall it if needed.
And the list goes on and on.
And on.

Am I crazy?
Maybe. I don't know.
Point being, there are lots and lots of ways to be protected or not protected. And this morning as I took the kid to school, I thought about a recent email fwd talking about all the clever ways bad guys stake out homes to rob later. Suddenly I was very slow to tell him my name or any other trivial small talk info that would give him any insight at all into my family - my kids, if they go to school, if I'm originally from Texas, how well I know the area, if I work, what my husband does, etc., etc.
Yeah, that was an awkward ride.
So, then, I guess the REAL point of this is a question -
when is it okay to put enough trust in humanity to do a good deed for a stranger?
or is it ever okay?
Because as soon as you do, you are making yourself vulnerable.
What a sad thought.