With Linuxchix, we've had reasonable success in providing the (fairly similar) "newchix" list for newbie questions, which I gather takes some of the stress out of asking potentially embarassing questions. The Linuxchix rules are "be polite; be helpful" so even the regular tech list is friendly, but I gather for many folk there was the additional concern that their embarrassing question would be archived for all to see forever, so the newchix list is not publicly archived. It's not a perfect screen, but good enough that no future employer will google your name and find those posts from when you had no idea what you were doing (and hold them against you).
"Stack Underflow" would totally work for those willing to admit to their ignorance in public, but some explicit "here's how to make a noob account that's not going to be associated with you otherwise" might go a long way to helping people be less embarrassed about asking, especially since pseudonymity sometimes just doesn't occur to folk until it's too late.