Like others have already noted, there is a difference between "professional" GLOs and "honorary" GLOs.
There are (4) types of GLOs:
* Social - e.g. Lambda Chi Alpha, Phi Mu, etc - mainly social, though there is a component of philanthropy/education/etc in there
* Professional - your Delta Sigma Pi's & Alpha Kappa Psi's of the world. In addition to the professional aspect, there is also a social side and some chapters are more social than others. One of my favorite Deltasig chapters was on the UT campus. Fun group
* Service - Alpha Phi Omega - they focus on service projects, but from what I've heard some chapters are more social than others
* Honorary - I was never part of one, but these usually recruited people from, say the college of business or education or engineering, that had a certain GPA. There is no "new member" period there.
I've never heard of Honorary GLOs doing bigs/littles or anything like that.