All very interesting but I do wonder at the value of these numbers in the end. The number of Facebook likes or Twitter followers is probably irrelevant to a greater degree - for example, does the size of the institution and the promotion of links/ids have any bearing on these numbers I wonder?
Ultimately it's down to what you do with the tools. Are these institutions engaging with audiences in two way communications, or are they just reposting press releases? How many site visits are resulting from a tweet, and to what end?
What's far more interesting from my perspective is what's happening at grass roots levels, where real communities exist and 2-way communication is viable. Tweeting revised library opening times in bad weather or service outages, building facebook communities of students on a new programme before they've even arrived to support orientation week etc.