The bearings usually don't fail to the point of seizing. These are journal bearing turbos and there is a healthy amount of oil lubing them. Normally if they wear they leak lots of oil. There will always be oil in the intake from the crank case vent recirculation though so don't take a small puddle of oil sitting in the intercooler as a sign the turbo is bad. More than 3/4 of cup, the probability is strongly towards yes a bad bearing. But the thinig is that the shaft is floating on a layer of pressurized oil so it can leak and still build boost.
Take a look at the VNT actuator replacement article to see how to isolate the turbo components.