I wouldn't class designers as geeks to be honest. They use a particular subset of computing technologies to achieve a goal but are hardly limited to the digital medium. To call them geeks is to tar them with the same brush.
Sure, some designers may be computer savvy and may in themselves be designers who are also geeks, but being a designer neither requires the traditional qualities of a geek.
I don't think geeks necessarily mean computer geeks.
I am compelled to link to Dorothy Gambrell's tidy comic detailing the difference between geek, nerd and dork.
1) Fundamentally typophiles are geeks, and "typophilia" is no different than any of the myriad other intellectual obsessions that geeks will develop.
2) Designers are accorded much more respect than traditional geeks, in part because it's much easier for the layperson to appreciate their work. (designers also tend to be better dressed, better looking, and more sociable than other geeks).
So in a certain sense it comes down to jealousy - here are people doing the same basic thing I do, but they're perceived as cool whereas I'm perceived as perhaps a little odd. That said, it doesn't help when they refer refer to my people as "flash boys and neck beards".