can anyone suggest reasons as to why a club should have a single webmaster as opposed to a whole committee having access to and adding to a website when they feel they want to?

I know of one club that the webmaster is not on the committee - the whole committee probably has to agree on what goes on the website and the administrator is passed the info.  It makes sense to have info put on by one person IMHO.  As a work intranet author I prefer colleagues to come to me and tell me what to put on their pages as then I can make it consistant with the rest of the pages. 

Are you speaking of one committee member being the webmaster?

As long as the committee have approved website content it makes more sense to have a single person in charge of inputting the information - it leads to a much more cohesive site and fewer arguments!

In our Win.dat site we all have an input and Chris is the webmaster as he has the best computer!!

A committee that has different factions (or cliques) could have a whale of a time if they could all put up what they wanted ;-)

Yes I agree were all Scout's and the other site I run is a Parish Council but some magazines I have had input to also have an editor (elected).

It depends on the type of website. Many websites are created with sophisticated programs like Dreamweaver or Front Page which require a good understanding of HTML, style sheets and various other aspects of web design. These kind of sites can only usually be edited by someone who has the same software on their computer and most importantly, understands how to it - it makes sense then for the webmaster to do all the updates etc on behalf of the committee, as I do for several breed club websites. I am about to convert one breed club site to a Content Management System (CMS) which will allow multiple log-ins so that others can do simple updates on particular pages but this wouldn't be possible on the sites I've created with Dreamweaver.

It can get very messy if more then one or two people are updating a website from different sites.  It's best to have one person maintaining the website who is easily accessable should anything need to go on that anyone can e-mail across.  :)