I forget the statistics, I probably used them in a YouTube back and forth somewhere, but in Florida alone over the past 5 or 10 years, something like that, there were thousands and thousands. Most were simply pot holes in the road, others were meters wide, others bigger still, but all traceable to the type of land they were found on, the tunnel networks, pipes etc, and none of them traceable to some other object in space.
That's what really amuses/confuses me about how proponents use them. The News wont report pot holes in the roads, but one massive, 20-30meter monstrous sinkhole is worthy of a minute or two, even if just to fill out the length of the show. As the only sinkholes that are shown to the public are then massive, you get a skewed representation of them and next to no science explaining them either (Science? In the News? Whatever next?).
Couple that with proponents doing absolutely no research themselves, the people who listen to those proponents similarly doing no research to double check anything, and in moments they are out and eagerly awaiting the next one to be found, using them as 'proof' of such and such, when it is only proof of their ignorance.
