One of the things that, I think, terrifies many people is having to admit their own ignorance about something. I think this becomes especially more pronounced when we feel like we should now something. Often, we hem and haw, and we even bite our lips and keep silent, hoping that, somehow, we will stumble across an answer (or someone else will do the stumbling) and we will be able to glean the answer through their challenge and then we’ll have it and seem smarter the next time around.

If you do this, stop it! Right now! Seriously! First, it’s annoying. Second, there’s a good chance the item you are ignorant about, others are as well, so you might actually learn something in the process.

An example from today… we were discussing something regarding URL encoding, and an example was given showing a URL and a string of characters in the URL. As we were discussing this, I felt somewhat weird, like I should understand what was happening. At first, I decided to play it cool, because I was sure someone would discuss it and I’d be filled in. That didn’t happen. As we kept getting deeper and deeper into the examples I started to get more and more anxious… what did this represent? Finally, I couldn’t take it anymore and I asked “so, what is the pattern being used here? Why does that pattern get us to this issue? I don’t understand why it’s formatted that way…” and trailed off expecting to be called an idiot or laughed at, or some other indignation.

Again, that didn’t happen. As we discussed the issue, it turned out that none of us had ever seen an encoding like that. I inferred that, from the way it was being handled, it was trying to take us to a location that we shouldn’t be able to go, but as to why that format was being used, I couldn’t articulate it. This prompted a bunch of us to experiment a bit, and see what happened when we tried different combinations. Net result, we were able to better articulate what the API should be doing, and what it shouldn’t, but we wouldn’t have gotten there if I hadn’t been wiling to admit my ignorance.
We always hear in Agile circles and elsewhere that, if you don’t fail, you don’t learn. That may be true. Academically, we may agree with it, but deep down, we really don’t want to fail. We don’t want to appear foolish. We don’t want to admit our ignorance. It hurts our pride, and it can be embarrassing! On the other hand, if we don’t admit it, we don’t know who else won’t admit it, either, so what the heck, take the initiative. Be willing to say “OK, I may be an idiot for saying this but…” You may just find out that you’re not as big an idiot as you think you are. Of course, there is always the danger that you (or I) might very well be. 
I don’t have a really good answer for that ;).