You will be depended on crispynews if you launch a successfull site. They will place their ads on your site. They can disable your ads "This is experimental, so this adspace sharing thing could change. For example, it may turn out that we can't cover our costs based on this fee structure". They can change their Terms and Conditions in any time. I think it's better to have own site, based on own or 3d party code, with full control on it.
EXACTLY. But for non internet savvy (or whatever you call it) I think it's a good start for them. A good example is WordPress and Blogger. If somebody wants a blog but doesnt' know the WHAT, WHEN, WHY.... then he could use Blogger as a start but then he knows well already as the time goes by, then he can have his blog powered by WordPress
The open source options are available at http://www.pligg.com -- though that URL seems to be dead this morning and a Spanish language project called meneame. Installation instructions for meneame are available here