We did earlier announce speaker for 2006-10-17 meeting: http://lists.balug.org/pipermail/balug-announce-balug.org/2006-August/000074...
So, in theory contacting would be a reconfirmation/reminder ... but I'm not sure if 2006-10-17 was earlier fully agreed to by the (presumed) speaker, or if it was suggested/implied, but not fully confirmed.
That earlier "announcement" also has text/blurbs that we can probably (re)use on the web-site, for announcement(s), etc., ... but probably also good to check with the speaker if there should be any tweaks/adjustments/changes (and various "short", "long(er)", and "bio" versions/blurbs are also quite handy to have, if we obtain such).