Despite Italy going ahead with it, I suspect it won't stand.
Italy’s Parliament today passed a new measure on web advertising, the so-called “Google tax,” which will require Italian companies to purchase their Internet ads from locally registered companies, instead of from units based in havens such as Ireland, Luxembourg and Bermuda.
The tax has stirred controversy, with some lawyers saying it probably violates European Union laws regarding non-discrimination over commercial activity and could be subject to legal challenges. Italy Goes Ahead With So-Called "Google Tax" [bloomberg.com]
I do not think it will stand either. It quite clearly violates EU law!
It may be a sign that some EU countries are getting fed uo with what Ireland and Luxembourg are doing, and may be a precursor to changes in EU tax laws.
The companies listed are the tip of the iceberg. Off the top of my head I can add Microsoft to the list of countries using Ireland to avoid EU taxes - although they, like Amazon, are not much affected by a law that only affects advertising.