Good thread!! Rather than address each post seperate, I'll try to give a general over view.
First off, are we talking about arms free or pinned?? Front or rear?? This of course will make a difference in what you can/can't do. Keep in mind, that there is the during and after phase of the bearhug. During...as you feel the attackers hands around you, you may have time to pin your arms to your side. After...self explanitory....hes already got you. You really dont know what hes gonna do until after he grabs you....he could pick you up, drag you to the ground, etc. One thing that you could do, is drop your weight. It'll make it much harder for him to pick you up. Of course, you have your hit to the back of the hand, headbutt, strikes to the groin, legs, stomps to the foot, etc. I would think though, that the attacker is not gonna stand there...hes going to be doing something.
As for the ground and why you need to fight from there. Well, IMO, everyone should have some knowledge of the ground. In response to TigerWoman...No, you dont need to go to the ground, but keep in mind, that at that time that he grabs you, you are doing grappling, only its standing. By not knowing what to do on the ground, could make a difference in the outcome, so to think that you will never get taken down, is foolish thinking. If you've never trained with a grappler, I highly suggest it. You're eyes will be open as to how quick you will be taken down, regardless of how good you think your stand up skills are. Keep in mind, that a grappler trains for that ALL the time, and the take down happens faster than you think.
I agree with Zorans post. Static techs. are only a part of the process. The techs. should be learned slow and then more resistance and aliveness added. There will be a huge difference in the way you'll have to defend yourself.
Chances are, you will be taken by surprsise. But then again, the same can be said about a shirt grab. Is the attacker going to stand there, or shove you into the wall??? Most likely it'll be the wall!!! Will that text book SD move be able to be done??? Probably not, but thats why its important to train with that aliveness, to get the feeling of what it'll be like. We can sit here all day and try to come uo with the "what ifs", but the fact remains that in the end, it'll come down to spontanious reacting at that given moment.
Mike