Any car with power going through the rear wheels, be it 4WD or RWD, will work better with either neutral rear toe, or slight toe in. If you run toe out on a driven wheel, as the outside wheel is the one with all the weight carried on it, it's going to get better traction than the inside wheel. That wheel will be fighting against the inside rear and will try to pull the back end of the car out of line. On a FWD car, this might be suitable to try and get some turn in, but i've never really driven or owned FWD cars, so I'm not sure.
As mentioned before, rear toe in will give you more rear stability under power. You might not need it depending on what you drive, but it's worth a try. I wouldnt say that it will induce understeer 100%, but I'm sure it has some kind of effect.
I think understeer is something that seems to be quite often misunderstood. The cars that I have loved driving most have normally had a small and very controllable amount of understeer to their handling when you really start to push them. Theres no such thing as a car that is entirely neutral in my opinion, and I think that 9 times out of 10, a car with slight understeer is going to be much faster than a car with slight oversteer.