Every runner is different from every other runner. Some participate in marathons to forever challenge their own personal best. Some challenge their best buddy. Some love the medal and some love the after-party and some love all of the above.
But the common theme is that pretty much every marathon participant adores a higher hill, a new place to reach, and a fresh thing to aim for. Meaning that there will certainly are and will be plenty of people on board for the LA/SF Challenge.
Now, about that consecutive order. No, you don't have to start with a particular marathon; if you ran the LA Marathon a few months back, then finish with San Francisco on July 29. If you start with San Francisco on July 29, finish with Los Angeles next spring (that date is lucky St. Patrick's Day, 2013).
There are a few to-knows, like you must have an official finish time for both. Good? Easy. Well, not easy. But you know what we mean.
Read the other details before making for San Francisco in July. And if you can't do that one, just start next spring in LA. And start picturing that new medal hanging from your medal rack. You have a medal rack, right?