Does a high number of anchor keywords diminish the backlink?

As I learn more about SEO backlinks I am faced with yet another question: If you include a lot of keywords in the anchor text of backlinks, does it diminish the contributing value of those words to the google index than if there are fewer words in the backlink? If so, how many words should I include in the optimal backlink?

I imagine a paragraph of text as anchor text in a backlink won't help those keywords much.

Looking forward to hearing more about it!

David

The question is really: what does a search engine consider spam? A whole paragraph being a link wouldn't make sense for readers, so search engines consider it keyword spamming.

Link for humans first, search engines second, and you won't have a problem. Link with just a few relevant keywords. In many places I notice people who sell links want no more than 6 words in the anchor text. I imagine the spamminess goes up after that.

Yes. Fewer words gives each word more weight.

The right number of words is the number it takes to describe what the link points to. Links are for human beings. Not for search engines.

(FYI, there is no magic number for words in a link so if someone tells you one they're full of poo poo).