That entirely depends on the mouth of the giver.

It is not so much the diameter of the member in question, it is about how wide s/he opens. If a person opens wide, the jaw becomes fatigued, tired, and achy. What works is to relax the bottom jaw and let the penis slip between moist lips.

Sometimes, there's nothing you can do. Some ladies have small mouths and no matter what, teeth will be grazing Mr. Happy. :(

It's really bad when it's the back teeth on both sides. But, such are the vicissitudes of life...

Short answer = yes.

It doesn't have to be. My GF's mouth is not big enough to give a full blowjob (she covers almost a third of it).
What she does is message it with her hand while focusing on the top third with her mouth.
The way she does it feels so good that in the first time she did it I thought she was deepthroating me (it was pitch black so I didn't see what she was doing).

Oh. It's so big around! My, it is thick. I can't fit it in my mouth. Translation: I don't want to give you a blow job, but I'll tell you you have a huge penis so you won't feel so let down.

Spot on, dlb.

My wife and I don't understand the common "blowjob". The woman is basically simulating a vagina when she does oral. If so, wouldn't sex be the same only better? The way my wife sucks is the way you'd suck your thumb. She basically takes it in her mouth and sucks on it like a pacifier. OMG does not even come close to describing the sensation.

Furthermore, my girth is immaterial. As long as she can fit it in her mouth, it's all goo.

Er, I mean good.

ViceRoy I would say that it is a mistake to try and imitate a vagina with the mouth. What we men want out of a BJ is the feeling of a mouth. Of course if we wanted a vagina we would engage in coitus. It's about variety. Along the same lines I am completely against the use of hands on the shaft of the penis during a BJ. If I wanted a hand job I would ask for a hand job-or do it myself.
Slightly off topic here, yes I know.

I have so much more control when I have a hold of it by hand, partly because I'm rather like Grim's GF, in that I can't fit much more than the head. If I don't hold the shaft I have trouble keeping the head in my mouth, and then what good am I? ;) It's also much easier to spread the juices all over it, which he LOVES, with a hand.

Hey, buddy - you got some fellatio - be happy!

what about gag reflex?....

Gagging? Tell him to stop moving. "Just lay back, enjoy it, and give it up!"