i agree with the two of yo, especially macd, but you will have to appreciate that for some new users, it takes more than just visiting the site once before they decide they want to be part of it, i for one, quite discovered techzim by accident, was in a rush, got the solution i wanted, and went away, i came back again, and realises, wow this is cool, but then again i didnt register coz i wa like maybe there is some protocol, maybe got learn some rules or something, then i realised everyone was free to participate and look right now, i am number 3(how the hell somersert toppled me from my second position after macd idk, but he has some pretty good answers though)
so all i am just saying is, people get hooked to websites differently, some are just looking for answers and honestly why should they coe back or feel obliged to participate just coz they received one answer?
i think the trick is for the admins and the senior members of the community to make the community so engaging and have a magnetic touch such as the same that people associate facebook with, so that they actually feel compelled to log in or "miss" the site.
having said that, techzim isn't doing a great job on mobile, 70%+ Zimboz use mobile, yet this site loads terribly on mobile, it costs a lot of people money, considering how expensive it is, to browse on a desktop site. nd the browsing experience isnt nice i tell you, i understand that there maybe such things as wanting ads to load, since they cant load on mobile, but using mobile guys, sometimes u cant eve see, the reply or comment button, i cant use my galaxy here u all know how they are notorious for chewing etym, so i use a bb 8520 curve and imagine the experience i get there, you can also imagine what its ike for most people who use fones like x2, and the thing is most of them use low budget smartphones...
in conclusion i think there is more that has to be done by the admin side to ensure users are kept engaged.