Having no experience with children, I do believe that 1 cranky toddler would be more than enough to frighten me. And now, demonic clowns.
Jesus, just the idea of demonic clowns scares me. Hence, 0. If that’s not allowed, 1.
Next up: penguins.
I think more than 6 penguins would have me nervously glancing around.
Next: hermit crabs.
(And incidentally, regarding velociraptors: I’m sure they were pretty nasty customers, but Jurassic Park exaggerated their size quite a bit for dramatic effect. One of them might hesitate to take on a full grown adult human. More than one, though, and you’d probably be dinner…)
I think about 50 would be okay.
Next: rabid evil bunny rabbits.
Seven. I figure I could kick some if there were fewer, and some would fight amongst themselves or [sub]ahem[/sub] make more bunnies, but more than six and things would get crowded and there would be no room to fight them off.
Next up, llamas.
Rabid evil bunnies? Ma, git out the stewpot! 
Oh, at least a dozen–some might try to bite me before I kill 'em.
Howza bout… Martha Stewarts?
None- she might actually try to make me clean my room so she could redecorate it. <shudders>
Next: worried, over-protective mothers (yep, they’re yours)
Worried, over-protective mothers generally have a dark underside that only comes out when you forget their birthday or Mother’s Day. Two is definitely tops in this category.
Next up is a two-parter: How many anal retentive Star Trek fans and how many rabid Star Wars fans could you tolerate in the same room?
I was at the Wizard World con earlier this month without any problems, so I’d say at least 150 of each and possibly more.
Next up: inchworms.
inchworms…about 12
dopers with beer
As many as want to come…so long as they share.
Next: lawyers
Four. I can only listen to three people argue at the same time.
Next: low-level political campaign workers
Depends, are they working for the Republican or Democrat trying to get elected? If they’re the former, I’d say about eight. The latter, two.
Next: People wearing Barney suits.
Yeesh. One Barney-suited person is plenty scary. Especially if you’re the only person around for him to annoy.
Next: mushrooms
Yeesh. One Barney-suited person is plenty scary. Especially if you’re the only person around for him to annoy.
Next: mushrooms
I swear to Og, I only pushed ‘submit’ once.
13 mushrooms would be scary. I have a recipe that only makes a dozen stuffed mushrooms. That extra one would just be there looking at me. :eek:
interior decorators
Depends on the make and model of mushroom.
Those little white puffball mushrooms you get at the supermarket? Not very intimidating: I’d have to say somewhere in the billions to be scary – preferably coming at you in an all-consuming tidal wave of 'shroom and spore.
Up in Washington they have these creepy Alice-in-Wonderland Fly Agaric 'shrooms which are creepy in clusters of, say, ten or more.
Bleeding fungus just needs one to be scary.
Okay Russian Nesting Dolls?
Any more than 2. Russian nesting dolls are vaguely creepy, especially if I’m forced to open each one and inspect the tiniest , nubby deformed one. Hate that one.
OK-howzabout fiddler crabs?
Fiddler crabs don’t scare me in the least. In fact, I’d take this opportunity to build a small fort and reenact that battle in Starship Troopers where they get overrun. Thousands of fiddler crabs. Unless they were flying fiddler crabs.
Here’s an interesting one: One-eyed, one-horned, flying purple people eaters