Because they're using these:
http://www.youtube.com/watch?v=GkfHC...eature=related
http://www.youtube.com/watch?v=cN5PY91sO7A&NR=1
They don't have to land, come to a stop, and be serviced by a ground crew between sorties;
They take 30 seconds to refill;
Costs less to operate than the 747 or 707;
There are two of them working the L.A. fires, each making two drops an hour.
There's a 707 working the fire as well (saw it last year at our local fire), but it takes an hour+ between drops.
But, heck, the state is broke, so Gov. Arnold was considering a cost alternative offered up by the state legislature, who wanted to send in hundreds of day laborers with these:
http://www.youtube.com/watch?v=v8J45...eature=related