They often offer something like 100% interest per 24h (or something similar). They commonly run for quite a few weeks (or months sometimes) before "they go scam" publicly. The obvious idea how to exploit them is to invest something small at the first day, withdraw it as fast as possible and repeat just with the interests from the previous bet (and of course take some money away from every successful round).
Has anyone tried that? Have you been successful? Is this kind of gambling popular/common. Has it name?
I don't think that such activity has good EV (expected value). You can't know for sure how long another scam will last. Add to this the fact of your "investment", i mean that you have some probability that amount of money that you will send to this will not be returned because it was to high for this scam (if you would send some small amount you would get
positive EV, but for sum that excess some amount you would get
negative EV)
So, we have
at least two probabilities, and the resulting probability of success will be multiply of two. And i think it will be very small

So can't say that this is good idea.