Before my new member class joined this past fall, our chapter was fairly small, but it has nearly doubled since then. With some people lacking in the participation department, however, one of our sisters commented that she believes we should be more choosy in who we offer bids to. It all goes back to what people wrote above about quality vs. quantity. Sure it would be nice if we had 100+ members like a couple of other sororities on this campus, but I have been told by some of those girls that they don't even know all their sisters' names, let alone recognize them on campus!
Even with approx. 70 of us, we make it a point to know EVERYONE's first and last name, as well as celebrating everyone's birthdays (although we do the "birthdays of the month" towards the end of the month for all of those with birthdays in the given month). We're all going to Chucky Cheese's for the February birthdays! Yaay, my birthday's in two weeks!
Okay, I've gone off topic again, but my point is really, do whatever you can within reason (call Nationals, etc) to help your numbers as long as you're not letting in any random Jane Doe just to raise numbers.