I think there are two opinions of Drew Butera:
1. He is horrible and should not be on any MLB roster, anywhere, ever.
2. He's not that bad, he just shouldn't be taking up a 25 man roster spot as a third catcher who has no value as a pinch-hitter.
I'm in the former, and if you read this Fangraphs article you may agree: Positional Power Rankings: Catcher. Keep in mind these are only projections.
At 0.1 WAR, Butera turns out to be the definition of replacement level, which many have pointed out over the threads. Why not pick up someone on waivers to replace him? Well, there just might be someone out there with some random chance upside whose floor is Butera bad. That person might save the Twins a couple hundred thousand.
But the reality you find as you scroll through the list is that few teams have third catchers any worse than Butera, and the further down the list you get, you start running into second catchers who are barely better. One example: Kelly Shoppach of the Mariners at 0.5 WAR. He's making $1.5 million.
The vaunted Rays have a 0.6 WAR player in the backup role, Jose Lobaton, and Fangraphs projects him to take nearly half the AB's at that position for the Rays. The Moneyball Rays have a 0.6 backup, as do the cash flush Dodgers.
In summary, I'd just say that having a cheap, solid defensive catcher as your third option isn't the worst thing in the world. I hope he's not on the opening day roster, but I don't have a problem with the guy being on the 40 man. Maybe he really is great at working with pitchers, and might be a real asset working with Gibson and Deduno at Rochester.