It's a very subjective thing.
1) Lets start with a simple example, a football match, which is offered by every bookmaker you can imagine. There is breaking news, that team A will miss a lot of their players due to a flu. Odds are dropping like crazy in all bookmakers, but there is one bookmaker that is slow and has bad software. While all bookmakers only offer 1.40-ish for team B anymore, that bookmaker still has the initial 2.00 for them. Is it ok to bet on this 2.00 ? What if a bookmaker is constantly slow with adjusting odds and you could regularly do it ? Not for 2.00 -> 1.40, but maybe 2.00 -> 1.80.
In my opinion, this is not a scam nor can it necessarily be called exploiting
unless you know it's a software issue and are intentionally using it to your own advantage instead of contacting the casino about it. I don't think it'd be right for me to call you a criminal for doing something you had no idea of.
If Amazon lists a $1k item for $10 by mistake, it's not my fault for ordering it. In fact, Amazon has had such glitches before and
admitted it was their mistake, proceeding with the delivery of the very cheap items. So in this case, it is the casino's fault.
2) By accident you discover that a bookmaker allows to parlay 1X2 and Asian Handicap market, which is of course a software issue. So you could parlay home win with AHC -0.5 for all kind of matches, which will give you good value odds. Is it ok to parlay these two dependant bets ?
I believe this is exploiting, although I am not 100% sure what this scenario is about.
Is it ok to take advantage of this software issue in general ? For $20 ? For $500k ? (Leave aside the fact, that LAngel played with "cheated" money).
No. Consciously taking advantage of a software issue is exploiting and scamming at the same time.
4) Lets say I have a trading bot (in betting or crypto exchange) and this bot goes wild due to misprogramming and I lose loads of money. Are all these users filling my orders scammers, when it's obvious that these prices are wrong ?
It's your fault. The buyers have no idea whether you wanted to sell your funds cheap or not and it's not their fault that you have misprogrammed that thing. Take it from another perspective: You go to an exchange and accidentally sell your ETH at $25 instead of $250. You clicked that Sell button yourself - is it your fault or is it those who bought your ETH so cheap to blame?
Where does an exploit start and a scam begin ?
An exploit begins when you consciously take advantage of something at one point and the scam begins when that "something" starts turning into a loss from your actions. Example: say Facebook has a limit of liking 100 posts per hour. You somehow manage to get unlimited likes and like 10k for 10 hours straight.
Facebook's servers are very strong and could handle your actions, but what if you find a glitch in a casino and can withdraw as much money as you can from it without having to deposit anything, so you take advantage of it and start withdrawing thousands of USD? The casino will at one point start losing money because of you. That's scamming.