I'm not sure what case the author is trying to make against RDBMSes, but SimpleDB doesn't seem like much of an answer. Shifting the burden of sorting and searching on to the programmer seems like a big step backwards to me.
SimpleDB shifts the burden of database scaling and maintenance from the programmer. Being free from those worries is a hugely important consideration. Even if it means having to forgo the ability to do joins or order by.
And you can still use SQL (albeit restricted) on SimpleDB with some of the new wrapper libraries such as this one: http://code.google.com/p/simplejpa/
Besides, what's so nasty about SQL?