From time to time people (including me once, a few years back) would ask questions like: what are the 'top' (or 'most popular' or 'widely used' or most downloaded) dists/modules on CPAN? Is there a download counter for each dist/module? Like this one from prz, a budding module author.
The answer is there isn't one, because CPAN is just a bunch of static files. The upside of this, CPAN is very easily mirrored (e.g. via FTP or rsync or offline via CDs) and served (e.g. via FTP, HTTP, or local filesystem). The downside, there isn't a place for much intelligence/logic on the serving side.
To implement this feature, we can put some stats gathering code on the client side, like what Debian has been doing for a while; in fact you can already see the list of most widely installed Perl modules from the data. Or we can add some stats to search.cpan.org like most viewed/clicked/downloaded dists and modules, and maybe top search keywords. Not representative of all mirrors, sure, but it's better than nothing.
Download counter, or at least Popular/Top Downloads, is a common feature on download/catalog/shopping/news sites, from freshmeat and Download.com, to Amazon and iTunes Store. So common that many users expect it to be there as a standard feature.
It's not hard to imagine why people like to know what's popular, what everybody else is using/doing, what's in, what's hot. It's a social side of human nature. And it's beneficial to know which modules are getting downloaded and used more, to direct development efforts to the more important stuffs. Volunteers can surely take the top modules list as one consideration when picking which project to spend their valuable time on.
What I'm not very clear on though is why, aside from PHP, many programming languages' communities don't like this particular feature? Do we hate competition, do we hate popularity contest, or are we just plain lazy?
Anyway, effort like CPANHQ might soon make the Top/most $foo modules, and more, possible. Yay!