www is default, client apps can add anything they wish, so www blog and some will be reserved, but you can also add services like even more advanced things like
Books (bookstores)
Songs (music collections)
Videos (you tube etc.)
The folks can build sites to host these on as well, but of course they are not copies but pointer to the data you hosted for instance. So you store your youtube collection and some site aggregates it all, many sites can use the same content (if some add in advertising then perhaps they wont be so popular 
)
not only locations for collections, also you can purpose structured Data for farther types, not dns but data types, which takes it much further so:
CAT (cat scan machine)
Xray
Robot
OWL (Semantic data (a bigger wikipedia type structure to ask questions to))
…
Anything devs can dream of basically.
And many more, so you can start creating networks of things as well as services like twitter blogs and so on.