Sharon, I would like to dwell on a somewhat different aspect. I will start with a platitude: it is all relative, and depends on the context. And I am sure I will get away with it! ;)
Seriously now... Just as in any relationship, there is that special cosy and comfortable, even creative, kind of silence that comes before the discovery, before the fun, before finding the solution - whatever you might have been looking for. I believe we all have our antennae well tuned to perceive it - and we don't feel threatened. In a 1-to-1 situation it comes quite quickly; in a class setting - almost as quickly, if the student base is consistent, and especially if you know them from your off-line contacts.
I think we have to factor in personalities, and that is much more than accounting for learning styles and predispositions only. Being an extreme INTP, I feel quite comfortable with people wanting or needing space - just because I know how it feels; I need space - LOTS of it - myself! However, when I work with emotional touchy-feely (metaphorically) students, I have to adjust and tune in to their wavelength - cos, after all, what matters is how and what they learn, and not how and what I feel. It is not too much of an effort but I do need to make the effort , and I have to be aware of the things I need to adjust in myself.
And then there is the ice-cold silence - when you almost physically feel indifference, lack of interest, hostility even, or, in a nutshell, the beam-me-outta-here-Scotty attitude... The "I'm_only_here_for_da_beer" (oh ok, for the paper) thingy... In all the 20 years of teaching I have NEVER encountered it in a classroom with EFL learners; but it has happened at least 3 times (that I can remember) during teacher training sessions. It was OK, you melt the ice, give them some time and they come over; but it always makes me sad because I think teachers get damaged by the system even more that students do, and the silence bubble is the best self-defence mechanism. Sometimes silence means you need to develop trust; my approach is respect, analyse, adjust and, well, it works out in the end.