Anyone have an estimate of how much of United's SFO-LAX traffic is O&D on both ends? Probably not too much, and it's that traffic that Virgin is targeting. I would still imagine that SFO-LAX will remain a huge route for the int'l (and domestic, I guess) connections at SFO for people based in LAX.
Also, the price-conscious SFO-LAX travelers already have Southwest. The only difference here, then, is an additional 5 flights, and first class. Still, I don't see it as being too big of a problem for United's SFO-LAX profitability.