I've gotta agree with ya there Rezzie, building that "human" bond in a linkshell is a bit more challenging when your members may or may not be there. That whole "Well my other shells are better for that." thinking breaks the glue that holds a shell together.
From a slightly different perspective though, if you get people together that aren't interested solely in the "EG" content you stand a better chance of building on the social aspects which in turn will strengthen the bonds for when you happen to be going for "EG" stuff. For instance lowbie xp grinding, easyish NMs for gear for those lowbie jobs(this with 2~3 ppl can easily be a few hrs where eventually you'll end up shootin the shit between pops), questing for w/e. If you build an "EG" shell and don't have the stats to say "We're among the best." the people you get will be either: People trying to carve out a name so they can join the #1 "EG"LS; People that come and go too sporadically to be in a dedicated "EG"LS. In either of those cases your kinda gonna be hurt, wether for members not being around, or for having members that get that name and then move on.

It's far more difficult to say no to people you "hang out" with and talk to everyday than to say no to random people that you just do "events" with.

Just a little off topic there^^