Hostile Mobs Do Not Spawn in Spectator Mode

In spectator mode hostile mobs will not naturally spawn. Even when summoned they will disappear. I was in Hard mode. I tried to go to gamemode 1, summon a hostile and then go back to gamemode 3. I was able to summon the hostile in gamemode 1 but when I went to gamemode three it (the creeper) disappeared. Is this intentional? (was testing in 14w27b...may be a problem in earlier snapshots).