Actually, not just wetnite dancing, but any disco dancing. Most people on the dance-floor hardly have co-ordinated steps, for that matter hardly dance 'well' - but still there is so much enthusiasm in the dance that it makes up for all that is missing. Most blogs, similarly, hardly have grammatical prose, but still the enthusiasm makes up for all that. Wet-nite dances are about dancing in groups, allowing oneself to 'flow with the beat' - blogs similarly draw on huge network effects - many of them involve inter-comments (quite unlike individual websites). Finally, dancing on the floor in a wet-nite comes to almost anyone - one needn't be a professional dancer - no one's looking at you. Blogs, similarly, are in the reach of all and sundry - no one cares what jabbering you put into them - and they are much easier to make than websites.
As a concluding observation, maybe both are outcomes of the individual's desire to express himself, to have fun - to be himself and to break free from society's need for 'professional' conduct. :P