I personally say as many as you want - keeping the following in mind:
1) If you are aiming to rank for some 6 word phrase - go for it - put 6 words in the anchor text. The amount of people who search for that term will be minimal, but hey at least you can say you are number 1 for something.
2) If you are aiming to rank for a 2 word phrase that is part of a 6 word link text, well the part of the algorithm that evaluates the link quality based on link text keywords would only value it at 1/3 as much as if it had two words (exact percentage will vary - it's just an approximation).
In summary - if you are trying to rank for a 3 word phrase in google rankings - use those three words. If you are trying to rank for a 6 word phrase - use those 6 words. Just don't expect you can get double bang for you buck and combine two different 3 word phrases into one anchor and get double for nothing - at best you will get only half value for each and could be less.
Re it being "Black Hat" - it's definitely not, just ineffective. "Black Hat" gets thrown around as a phrase all the time for all sorts of things that aren't. Black Hat implies doing something tricky or against the rules that cannot be easily discovered, in order to rank. It is basically trying to "outsmart" google's robots by doing things that are clearly against the rules of Google, in a way that will be difficult for Google to discover. Black Hat stuff is usually effective short term, terrible long term.
This theory of lots of words is not against the rules, it's just ineffective, and it's not sneaky or clever enough to be called Black Hat!
Hope this helps,
Matt
Marketing Web________________________________________
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