I'm no UA apologist (LOL!), but this story (which I didn't read!) seems to be an exaggeration based on what's posted in this thread. I book a lot of travel for family and friends -- some of it a day in advance, some it 300 days in advance. I can basically tell you which seats are 'blocked' on a given aircraft. And it's not many (unless you believe that SHARES is smart enough to go in at some point between 330 days out and N days out and block some seats.)

For example, on the Airibi, the aisle / middle bulkhead seats are blocked until time of check-in. Why? Dunno, but probably for disable pax or something. I believe they also block a couple seats right in front of the rear lav. Why? Dunno -- cause FA's need a place to read People Mag??

But the bottom line is that there are a lot of underhanded tactics employed by UA, but this aint one of them. If a seat shows as occupied, it almost certainly is, with the rare exception of the seats I described above.