That is, at the very basic level, what gamification is, its making an activity into an activity with specific measures of progress toward a goal, such that people can rank themselves (and we do).
This isn't a new or faddish idea, its an insight into how people act, and an attempt to use that bit of new understanding, as Atwood did, before being aware of the term, to engage users using what are called 'game mechanics' which are basically motivations outside of the actual reward structures of the activity. I suspect "engage your users" is moving into the much more targeted and practicable mode of "gamify your interface" rather than vice versa.
Furthermore, "gamification" by that definition often begets "gaming" the system. Because scoring, measuring, and mechanical details almost never perfectly match the spirit and original intent of the game, these edge cases cause dissonance and frequently disengagement. Examples: A baseball player hitting 17 foul balls waiting for a good pitch, basketball players causing fouls on purpose simply to stop the game clock, monks in Everquest using the "feign death" skill to split mobs that would be unbeatable as a group; these are real dynamics in successful game systems originally designed or evolved to be that way. In other areas, such as academic grading or pay-for-performance, the dissonance is significantly more profound.
People play foldit because it's fun, and that's what "gamification" should be about. The scoring metrics are merely a small piece of that.
Stack overflow's design isn't about making it fun, its about making the users collaborate into something that is easy and valuable to the population. The rules of a game in general aren't about making the games fun, they're about providing a framework for competition.
Sure, designers will continue to include game mechanics to enhance engagement, it just won't be this crazy concept that everyone obsesses about. It'll just be a tool you can use sometime if the situation seems right.
And I disagree about stackoverflow on both counts. I believe it is fun, and that competition is a nonessential component to the sites success. Some people do thrive on competition, others do not. The core of stackoverflow is the dialogue between askers and answerers. Maybe say "rewarding" instead of "fun." The scores and rules are a nice enhancement to the core experience-- they facilitate public recognition, sorting and organization, among other things. There has been competition and recognition on Wikipedia for a long time, and they have made no overt attempt to "gamify".
Another important thing that the stackoverflow game mechanics do is guide users to functionality they might not know about. What you call "driving" users I would call "leading." Hardcore completionist, achievement-oriented, and competitive users are, of course, driven. The rest, however, are not, and to them features like "badges" just bring attention to the wide variety of ways the site can be engaging. The FAQ is well-written and very useful. The "analytical" badge merely helps draw a little extra attention to it. vBulletin has a boilerplate FAQ that probably no one has read in years since it's the same on every single forum that uses the software.