I am wondering if it is wise to indiscriminately block
wget on servers that I maintain.
Has anyone experienced unintentional traffic overload due to clients' use of
Wget does no more and no less than an actual web browser with the only exception that it can be told to suck a whole site down which it can do without delay and which on a real web-browser is just about impossible to do quickly. I often use it, for example, to grab data in a particular directory hosted at a site as for some jobs it's much more efficient than using FTP - the URL directs it to the right subdirectory. Such use actually reduces the total resource utilization and it's completely legitimate.
Therefore, if there is justification for doing web browsing or FTP, using wget should be viewed as just another form of browsing; I would not block it, no, at least not indiscriminately.
I would look for individual users who may be causing a problem and have a talk with them. Or, push it to a lower priority using OS tools.
It really depends on your site. If it's full of information that one might want to have at in larges chunks but doesn't have FTP then you probably should not block it. On the other hand if it's something like forums or blogs or a product website then absolutly block it if its causing trouble. Certainly no one plans for a multitude of users inhaling your entire site at one fell swoop, and if it's overloading your site then even if there are legitimate edge cases I'd block it.
In short as an admin you you take the steps needed to ensure availability of your servers, if that means blocking off wget then that's what's required.