One of the things that probably annoys some users of JoeUser (bloggers in particular) is the syndication of other articles and forum posts into their blog. 

Why did we do that?

the goal of JoeUser is very egaltarian.

When I'd set up JoeUser as my personal blog I saw the pros and cons of blogging it alone.  As it got more popular, I became aware of a barrier to entry into the wider world. Basically, my blog was at the mercy of an established order of elite blogs. It bugged me that even if I wrote something of high quality (IMO of course) that I was at their mercy as to whether they would choose to link to me or not.

Most bloggers out there have very very few readers. So when I decided to open up Joeuser to the public, we came up with a system: Have new articles show up on all sites so that readers of one would be inclinded to go to others.

This has the negative side effects you described. Our plan though is that users will be able to buy premium accounts this Fall, which amongst other things, will give htem greater control over their blog.

Ultimately though, the concept of Joeuser revolves around the premise that most bloggers get few readers and provides a system to rectify that.