It didn't happen on the two flights I just had. And I've never seen any kind of issue when flying SW. Here's the thing. Yes, business travelers can be tough nuts about seats. But, the vast majority aren't going to get into an argument about taking a window seat in row 3 when there's one open in row 5. Nor are they going to care about taking a middle seat that is being saved. Most business travelers want the aisle seat.....those aisle seats are not often saved seats! Doesn't make sense. People sit in them and then save the seats in the middle/window.
Not to mention that a lot of business travelers (traveling on business accounts) are flying business select, which means they are boarding before EBCI people. And, many of the front of plane seats are taken by med preboards, then by business select people. Most people that are saving seats tend to end up further back.
I'm sure there have been instances where an argument has happened. But, if someone is saving a seat, or two, in the same row they are seated in, it just doesn't seem to be a huge issue with others. Now....if they are trying to save seats in the row across the aisle, and the row behind them? Yeah, all bets are off.