Replicator quoting research which shows that people who customize their car (from bumper stickers to whatever) are more likely to engage in road rage.  The logic is that the customization is indicative of someone that thinks of their car as personal space and more easily tilts when confronted with bad driving.  I didn't read the study (written by CSU profs and published in the Journal of Applied Social Psychology), but I can only assume that this is a correlation and that no causation was implied in the study.

In the world of web apps, we're all searching for that secret sauce that makes a site "sticky." Features that allow customization are often considered sticky. This logic seems to assume, at minimum, that customization of a thing reinforces strong feelings for the thing - if not outright causation of those feelings.

It would be interesting to know if the more bumper stickers a driver had, the shorter their fuse…  If so, I have another theory to explain the observations.  Perhaps the causal agent of road rage is insanity and all that's really illustrated here is that folks with lots of bumper stickers on their rides are a little nuts.  Perhaps the same can be said of folks with lots of Facebook apps?