I had a couple of outlets go out in my house. I went to change them and to my suprise I found Scotchlocks instead of wire nuts. I have been a comercial/industrial electrician for about 14 years or so and have never seen this. I do know sometimes residential wiring gets done a little half horsed so I called 3M thinking maybe this was sometimes practiced 30 years ago but of course 3M said 12 volt only. I plan to change it all out but wanted to know if anyone here has seen this before, other than automotive anyway.

You mean them dodgy things they use to "tap" into wiring looms in cars?

I've never liked the use of them even in the application they were designed for, let alone in a house!

Those be the things. i have used them in various vehicles of mine but never on 120v. Heres a pic-

http://site.innovationestore.com/images/family.php?id=3m-scotchlok-electrical-idc-804

Yeah,
That's them.
Designed for those that can't use basic hand-tools like strippers and screwdrivers.

In a home? Never.
Mid -late 80's, thats all we used for our temp lights. Run the NM and strip back at the bulb location and use these with the pig tails.

We use them in continuous row lighting applications, and never had a failure.

Model 567 is rated 600V general purpose and 1000V in signs and fixtures, #12 Run and #18 Tap.

They're a lot faster than to cut, strip, and wirenut all the connections

3M calls them "insulation displacement connectors"

I see those in homes all the time and they always give trouble.

I see them often, inside flourescent light fixtures for the ballast connections. But, I have never seen them in general wiring, though.

20 years ago, somebody was marketing connectors like this for ballast replacements. I haven't seen them since.

Those "no-box" AMP NM connectors they use in modular homes are also IDC connections. You can bury them behind the drywall according to U/L. There was a time when AMP was saying you could use them in general wiring, fished etc. The code didn't change (334.40(B)), only the marketing.
It always smelled pretty fishy to any inspector I talked to. I talked to an AMP rep about it and he sent me a few. (I may still have them around here somewhere) They are not much different than the Scotch Lock in my opinion. The last time I saw an ad they were only targeting modular homes and citing 552.48(N) and similar.