How common are they anyway? It seems like we see more of these things than we used to.
Yet another one, up on Chicago's North Side. Looks like it swallowed an SUV whole.
http://www.chicagotribune.com/news/local/breaking/chi-car-tumbles-into-sinkhole-on-northwest-side-20110820,0,765202.story
There had been a sinkhole that was plaguing US 422 through Palmyra (http://www.pennlive.com/midstate/index.ssf/2011/04/palmyra_sinkhole_under_repair.html), but it must have been finally fixed as I've seen nothing about it from PennDOT since April.