It seems that the spawn rate of legendaries, while lower than that of other pokemon, is still quite high. So far today, I've witnessed about a dozen messages indicating a rayquaza spawn, two for moltres, and two for zapdos. Even considering that some of them spawned inside trees, and other hollow objects that make them unreachable, having 4 rayquazas, a moltres, and a zapdos caught between all players in a day seems a bit high. Especially considering there being only about 3-6 players on at any given time for this to happen.
Edit:
Spawn rates still going strong.
