UA1858 SFO-DEN was oversold by 12 at 3 hours til departure. Flight went out exactly even. I was first up to take a $400 voucher to leave 2 hours later with a confirmed seat in F... oh well. Many of those that didn't board were local check-ins ... it's insane how many people buy tickets, check in, and don't show up (or show up late and get stuck in security)...... Tough to get VDB's on the 777 flights anyway...