There's a particular sort of self-publishing that I think is a Good Thing, which is the personal homepages of iconoclasts. These always seem to eschew off-the-shelf Content Management Systems, which of course basically didn't exist in the 1990s when a lot of these sites first sprang up, and they're not maintained by the sort of people who'd use someone else's CMS anyway.
Over time, the sites gather a collection of essays and other amusing and diverting or informative material on a range of slightly connected topics; there's a selection effect here - if your opinions are conventional or not worth sharing, you don't have a website for offering them to others.
Before the internet, these people would be the local village oddity - now everyone gets to appreciate them.
Here's a representative sample of my favourites:
* Xah Lee
Wikipedia has long allowed people who have never met to write an article together, and some of its articles are very good. Wikipedia has a considerable quasi-judicial dispute resolution procedure for when editors can't agree. Sometimes you just have to compromise with liars and idiots.
Github, on the other hand, allows each editor to have his own copy of an article or group of documents, and choose which contributions he includes. If the original creator of a document is him or herself an idiot, or just loses interest, then any other editor can promote himself as the new preferred source for updated versions of the work. The Open Knowledge Foundation has recently assembled a group of authors to write the Data Journalism Handbook; collaborative editing has been possible for centuries, but there is now no requirement whatsoever for reliance on a central co-ordinator or editor of the contributions.
Effectively, this means people can now share out the work of writing something amongst interested competent strangers. This implies that it is now possible to write a detailed policy analysis of a matter of public concern without having to work for an NGO or otherwise organise paying someone to co-ordinate efforts; people's spare time can now be aggregated without the need for them to trust the aggregator.
I am going to use this to attempt to crowdsource a detailed criticism of the European Union.