It's a slippery slope.

What rules are you breaking to do your favor? What rules do you expect someone else to break for the return favor? What rules might they later expect you to break? To what extent do you stop seeing the rules of external society as rules that you're supposed to follow?

It starts as favors.

By the time you're stealing from your employer, it's blat.

By the time you're recruiting one friend to submit paperwork to help another friend commit insurance fraud, it's still blat. But also its starting to look like something else.

Once you owe a favor to a Mafia Don, it's called organized crime. But the underlying blat is still recognizable.