I actually like Mos Eisley. It was familiar in a good way the first time I saw it -- I could totally picture it, although I haven't actually come into chat, except once to talk with Gilles. Heh, I fear it would be like Luke and Obi Wan walking into the cantina -- a stranger! Anyway, I like giving things names IRL, so I thought, if it's okay, that I'd make some comments.
I had no idea what an ansible was until someone upthread defined it. It would be very obscure to a lot of people. (This is why I think Mos Eisley, or, say, the Federation or the USS Enterprise works well -- if you don't know what Mos Eisley et al is, really your geek credentials should be revoked ;) )
I did want to note that it's not just the Sci-Fi stack, it's the Sci-Fi and Fantasy stack. I think both are complimentary. So something that is represented as purely and exclusively Sci-Fi just might dissuade a fantasy-oriented member (like myself) from joining in on chat. Conversely, I think to suggest something like Todd and Steve's Fantastical Stargate, TARDIS Talk, The Prancing Pony, or the Department For the Encouragement of Magical Chatter and Friendship errs way way too far on the fantasy side (and is silly to boot).
It occurred to me that something with the number 42 in it might be ubiquitous enough for the Sci-Fi/Fantasy community as a whole, for HGTTG is certainly softer sci-fi than, say, The Time Machine, I, Robot, or 1984, and includes some fantasy elements. If the name of the chat room is super-specific to, say, one episode of ST-DS9, or is a term that is meaningful at first glance only to a select few, it won't be inviting to the Sci-Fi/Fantasy community as a whole. I actually like The Bridge (but, you know, we gals love to chatter while we're driving -- car, hovercraft, broom, Federation starship, whatevs!)
There are sometimes gender differences, I think, in how women and men approach Sci-Fi and Fantasy, so I think a name that is inviting to both sexes would be ideal. I guess I just wanted to say that it's not just Sci-Fi and it's not just guys.
If you made it through my post, thanks for listening and giving it some thought if you do :)