What you are saying makes sense except that I don't think the online books get the kind of action and want the kind of risk to exposure that you are talking about when it comes to MMA. I'm assuming that's why so many of them are so seemingly quick to limit a lot of us. I'm not limited (that I know of) at 5d now, but I was. And I wasn't even betting big sums, not 4 figures ever.
The reason for limiting is to have a better handle on adjusting lines. Sportsbooks in Vegas will also limit certain players if they are known winners. They’ll take their money, with the stipulation that they can adjust the lines between every bet. I know some people who can’t make $500 bets anymore without getting an “okay” from a manager. But I guarantee you, if I went to make a $500 bet at the same book, they’d take it, no questions asked, seeing as they have no idea who I am or how good of a gambler I am since I don’t make bets in Vegas. Online books are the same way, if you’re withdrawing money and it’s setting off a red flag in their system that you’re a “winner”, you’re gonna get the short end of the stick
In other words, I think they are fine with limiting the amount of action vs getting more action but also leaving them way more exposed (and exposed theoretically to the people that know what they are doing). Because of the limited amount of action they get on MMA (relative to other sports anyway), they may not be able to cover their exposure if they misprice a line and a bunch of sharps put big $ on it right away.
I mean, in a lot of cases we are talking about fight pass prelims here right? Where the amount of total $ bet on them is probably extremely small, relative to other events they take action on. If they misprice a guy that should be +125 at +250 and everyone here jumps on him all the way down to +125, they may well never get enough action the other way to come close to covering all the $ bet on that guy. And so they limit people on openers sure, but if they are doing that and only letting me bet $100, how important is handle to them really?
I can almost assure you that fights on the prelims, that inherently have more variance to them for a multitude of reasons, have lower thresholds to induce line adjustment and movement. Like I touched on in my previous post, if a +250 fighter is going to be hammered by the public, only a small amount of money is going to be bet at +250 before it is adjusted. Look at how quickly we, as a thread, bitch about someone hitting openers and ruining the price for everyone else. In none of those situations are thousands of dollars being wagered, either.
I am guessing it probably varies from fight to fight, the amount of action they expect, etc. I'm theorizing here of course, I don't know for sure what their actual philosophy is.