That's ironic - I read the same article you did, and came away thinking that it was a puff piece on A16Z.
There are lots of negative things you can say about Ben, Marc and the others in the name of "Balance" - and other than saying "They are paying a lot for companies" (which isn't even an indictment on them, just a description of their strategy) - I didn't see it.
I'm surprised they didn't mention Instagram/PicPlz in the article, that was a bit of a stumble (though for honorable reasons)
That said, it's certainly possible that AH are inflating rounds. (this is different to overpaying)
Github's Series A raised some eyebrows, but yet they are growing phenomenally, have loads of revenue, and have an exceptionally talented team.
However, it's doubtful that anyone currently knows whether today deals are justified. We may need to wait a few years, until more exits materialize.