You're talking about the 265 weight limit, right?

They do that at BJJ tournaments. Sometimes they make you weigh in moments before you step onto the mat and if you're over by even half a pound, they can disqualify you.

I think that puts a lot of liability on the promotion to utilize that in MMA. What if one of the main event fighters warms up, but doesn't have any water because he's afraid of missing weight immediately before a fight, he either runs the risk of feeling like crap throughout the fight, or the fight has to be cancelled because he drank water? It's a lot of unnecessary stress, and ultimately wouldn't work if you want fighters to be at their best.

Regardless of when fighters are asked to make weight, it's their responsibility to meet those obligations if they said they would. There's nothing wrong with day-before weigh in, some people just like to abuse it, and they ultimately pay the price like Anthony Johnson did.