The Steelers gave up over 100 yards in penalties- though some of those were total bullshit- and were trailing most of the game. The offense was looking good, they just couldn't get anything substantial done. The defense, on the other hand, created numerous opportunities, and got San Diego to cough up a safety. Both teams also missed one field goal apiece, due to crappy weather and field conditions.
The game had a crazy ending, too. San Diego had five seconds to do something. They tried to move forward with a bunch of rushes/lateral passes- one of which was tipped by Polamalu, recovered, and taken to the end zone for a TD. Oopsie! So, the score had been 11-10, it went up to 17-10, zero seconds left on the clock. The Steelers get ready to go out and kick their extra point, but then the play went under booth review. It was determined that one of San Diego's laterals had actually been a forward pass (really?), which invalidated the whole play, and the Steelers couldn't decline the penalty. So, even though San Diego was the guilty party, the Steelers lost their extra six points and went back to winning 11-10.
To give you an idea of how fucked up the last play was, here's the "box score" version of what happened (found on Fark):
1-10 SD21 (:05) (Shotgun) P.Rivers pass short middle to L.Tomlinson to SD 24 for 3 yards. Lateral to C.Chambers to SD 26 for 2 yards (T.Polamalu). FUMBLES (T.Polamalu), RECOVERED by PIT-T.Polamalu at SD 12. T.Polamalu for 12 yards, TOUCHDOWN. The Replay Assistant challenged the backward pass ruling, and the play was REVERSED. (Shotgun) P.Rivers pass short middle to L.Tomlinson to SD 24 for 3 yards. Lateral to C.Chambers to SD 26 for 2 yards (T.Polamalu). FUMBLES (T.Polamalu), RECOVERED by PIT-T.Polamalu at SD 12. T.Polamalu for 12 yards, TOUCHDOWN. Penalty on SD, Illegal Forward Pass, declined.
What's neat is that, in the entire history of the NFL- over 12,000 games- there has never before been a final score of 11-10.
ETA: Now the ref says he made a mistake, and the final TD should have counted. Grr. At least we still won...