This must be why I always Uber to the airport. On normal days (not big travel day like Thanksgiving time) you can get from SoMa to Standing Outside SFO With Luggage Out of Trunk in about 30min during the day. I've seen as low as 15min at night.
I may have always gotten lucky and when I actually plan the trip I try to go for more like 45min travel-to-airport-time. Just to be sure.
On Thanksgiving or such, the off-ramp from 101 to SFO takes about an hour. That's crazy.
Here's a map with travel times: http://www.trulia.com/local/94128/driving:1%7Ctransit:0%7Cpo...