Im actually puzzled by the preference for having a seat saved by a person rather than a towel, t-shirt, etc.. For someone who is just taking a break in between sets to visit the vendor room, restroom, or signing line, Id rather see something in their seat to show its taken rather than walking halfway down a row, only to be told that every single empty seat is being saved.
On the other hand, if you save a seat without intending to return for the next band, that sucks regardless of whether your seat is being saved by a significant other, friend, random stranger or a towel.