Double spending is so very difficult to do, if at all. I wouldn't even be worried about it. I mean when's the last time this has even happened ? I haven't heard of double spending forma very long time.
Umm, pretty recently? Double spending happens every day, and most people don't really look into it. Why bother anyway? Blockchain.info has a list of all double or triple spent transactions, I will see if I can find it. Double spending is definitely possible and even if it happens infrequently, it must suck for the gambling site owner to have to pay out a win that could have easily been double spent if he lost.
there is nothing to find it is literary on the first page of blockchain.info
https://blockchain.info/double-spendsand i gotta say this is not a serious thing, nor a common thing that happens. look at this page and look at the
dates and times the newest one is from yesterday. so it is not like people are double spending thousands of tx!!
also i should add that from all that list not all are fraud. there are times where you double spend to include more fees for your tx to get confirmed.
p.s. this is avoidable easily with 1 confirmation requirement.