There is a whole "Theory of Donking" (eg. Andrew Seidman - "Easy Game"). The funny thing is that donk betting "hides" the range of the guy who is doing it (sort of). For example, if you take 3 players. One does not donk and has Fcbet: 33%, second one donks: 50% and folds to cbet: 66% and the third one donks 33% and folds to cbet: 50%. Now, how much % of hands does each one of them continue with? If you do the math, it turns out that all of them continue with the same amount, about: 67% (so they fold 33% of hands). You can really figure out alot from stats of the player who donks, but from my experience donk leads by
* weak players typically signify weakness (especially if he donks alot, mindonk bets etc)
* aggro players/regs signify polarization (air/nuts)
* nits...we know what it means (NUTS!!!)
Some players like to lead with flush draws (they try to set themselves a lower price to see next card) and sets (to get more value, especially when thay can be outdrawn).