This article reiterates 2 of my favorites points --
1. the lack of real-world transactions, coupled with
2. the fact that these transactions are usually done via 3rd party processor or immediate conversion back to USD. If vendors had faith in it as an actually currency, they wouldn't feel the need to do so. This is not true adoption, this is simply an attempt at expanding one's market by accepting a tradable item.
Glad to see some more sobering articles emerging as I've been wondering why no one has coherently written these things. Most of the negative BTC articles on HN are poorly written and used as a straw man.