Semantic MediaWiki can basically be coerced into doing whatever one wants. It’s powerful, and pretty easy to use, and works well for situations with lots of different types of things. The question is whether it is actually suitable, half the time.
Like a blog, for instance. Why would one use SMW over (say) WordPress? It seems to come down to how many other things one wants to do with the system. For example, blog posts might have photos attached, and if one wants to treat those photos as items in their own right (with authorship information, location, and other metadata, perhaps) then a straight-out blogging platform isn’t going to do that as flexibly.
See? I’m just trying to convince myself! I like MediaWiki…