As the person who started this one running some time ago I would like to offer 
some comments

I referred to an unsourced entry in Wikipedia because I had come across it, it 
may have been relevant to the topic and it may have produced someone who 
did have a source for it.

Wikipedia has all the virtues and all the vices of the internet and of humanity. 
It is not a primary source. It is of variable quality, as are books and journals. 
You may need to apply more critical thinking when using sources from the 
internet, but you don't turn off that facility just because something is on 
paper.

For "amateurs" such as myself, (MA Cantab) who do not have easy access to 
academic libraries the internet can be a good source of material. The posting 
of primary material enables data to be found found via good search strategies 
that would never be found in a paper library. 

The real tragedy of the internet is that there are enormous resources out 
there beyond Wikipedia which are little used. The Education Minister here in 
England has just encouraged pupils to use Wikipedia because "they don't have 
access to traditional sources". It seems that nobody told him that in Somerset 
where I live if you have a public library card you have online access to, inter 
alia, OED, DNB, Grove (Music and Art), Britannica (3 levels), The Times and 
various OUP journals.