All the electrician manuals say if the "receptacle" (that's the fancy name for "holes") is not actually grounded then you must use a two prong outlet, so that the user doesn't think it's grounded when it's not. Oh noes! You lied to me about grounding! What the hell am I going to do if I have a 3 prong dealy to plug in and only 2 prong outlets, I'm not going to say "oh well, I guess I can't use this because I don't actually have a ground", I'm just going to use one of those little adapter dealies. (*)
Oh, and that little tab on the adapter where you can run your own ground is a huge lol. Yeah right, adapter, like I'm going to plug you into the wall and then run a wire outside the wall out my window and hammer in a 6 foot iron spike so I can be properly grounded.
I mean, when the fuck do you need grounding anyway? Our electric service is not sending massive lightning surges into the house at random intervals.
The worst thing about the two prong holes is just that plugs don't stay in them. The grounding prong is really just to hold your fucking plug in the holes. The only time I've ever seen scary sparks from receptacles is because of the two prong dealies not making good contact and pulling halfway out and bending the prongs and so on.
Our house has a mix of old knob & tube wiring and newer stuff. Any electrician who works to code is not allowed to touch the old stuff, their only allowed action is to replace it. So I either have to do the work myself, or hire someone who will work under the table.
It turns out that hiring people to work under the table is not actually hard at all. So far I have yet to encounter a single contractor who insists on working to code; in fact they all say something like "I could do this to code but it will cost you 25% more". Okie doke. (I imagine some national chain guys would insist on doing it by the book).
* = you see the same sort of daft behavior from library writers all the time. They think they are being "rigorous" and "safe" by not providing a function to the user which is maybe a bit dangerous to use, or maybe doesn't do exactly what you would hope it does, but it's retarded. What do you think the user is going to do? Not write code in a way that needs that function? Pfft, of course not, they will just write their own version of the faccility you failed to provide, but their version will be *much worse*, so by being "safe" you have actually made the final product worse.
On a semi-related note, I just got a washer & dryer, and of course the delivery guys won't hook up the gas. It's funny/ironic that because of liability fear, they won't help you with the bit that's actually dangerous and could use the touch of someone with experience (the main issue is knowing how tight to tighten the fittings).
ADDENDUM : well I tried to ground the computer outlets, but it was way too much trouble. I would need a flex drill extension, which is not that hard, but then I would have to worry about what exactly it is that I'm drilling through inside the wall that I can't see (maybe some dental mirrors would make that safer), then after that there's a hole you have to try to thread a wire through it from outside the wall. No thank you. Grounding is over-rated.
Some A-hole at some point ran new romex into the walls, but didn't hook up the ground line of the romex to anything, and then installed two-prong receptacles. That's legal code and all, but it's fucking shitty. It means I can put in a three-prong receptacle and hook up to the romex but I have no ground. And I don't know where the other end of that line is to get to it and try to attach it to something. All the lines go through the basement so it would have been easy to just run it over to a water pipe. They put in a new duplex box so they had the wall open and could have done it but didn't. Fuckers.