I tried to go though most of these posts before responding, and one thing I kept seeing was that Jean Luc Picard is referred to as Picard, William Riker is referred to as Riker, but Geordi LaForge is referred to as Geordi. Where Picard and Riker are stronger figures on the screen, Geordi LaForge shines in a way the other two can’t. Here is a highly competent and ambitious man who is so friendly and personable that we are all on a first name biases with him. The VISOR hindered this not at all. Major kudos to Levar Burton for his fantastic work.
I suppose on the name thing it's one of those things where "LaForge" is too "last name sounding" to use as a name. Picard, Riker, Crusher, Troi all are pretty smooth sounding names that, reasonably, can sound like given names when used. "LaForge" just screams "last name" as it's not very phonetically pleasing at least compared to "Geordi."
Somehow Chief O'Brien's last-name sounding last name disproves this theory but, then, it's a "smoother sounding" last name (probably because the main part of it sounds like a first name.) "LaForge" just strikes me as just not pleasing to say when referring to someone. "Geordi" fits better.