Yes. A vampire who uses his or her dark form constantly should certainly scare Sims who doesn't have the brave or occult-loving trait. As others have suggested, this could cause responsible Sims to contact Vampire hunters (which could consist of any Sim that has the brave trait). These hunters have special amulets on them that reduces the Vampire's energy, forcing them to flee and recover. A strong vampire can resist longer and risk putting few of them to sleep to counter the energy drain. Get them all but one to sleep, and you could feed on the last one, just to send a message. Most likely beyond anything they'd do, but one can dream..
(Vampire Hunters could also use Werewolves, if they ever bother to grace us with their prescence, and have the vampire run or risk fighting an equal or tougher predator).
And now I'm picturing my Sim Vampire chasing hapless Sims down the streets in batform.
Also, have Sims actually sleeping when your vampire breaks in during the night, and make the vampire able to drink their blood, or hypnotize them to get up and then drain them. Next morning, the bitten Sim will be uncomfortable, and other possible residents of the house will be scared.
