I see quite a few comments trashing this article, why?
It gives solid advice while reminding the reader that this is not perfect.
If I was Snowden this is not enough at all, but If I was an illegal immigrant in a country full of others like me? I think this article plus the final note about past data, does actually give a very solid advice.
I would argue that those who follow this guide, and take to heart the final notes and does something about past information (e.g move to a new address, change some habits, etc) would not be discovered in a mass deportation. Again, if you are an individual who is uniquely targeted by a government, this is not enough.
And yeah, they missed some points and this isn't perfect, but anyone who is serious would do more research anyway, so I actually think this a good article.