关于链接文字的讨论

 看到几个英文帖子都是关于链接文字的，总结一下：
1，链接文字的重要性：
1) Anchor text is extremely important to rankings, especially in Google. Ive seen some evidence in Yahoo, but not to the extent that Google rankings can be influenced.
2) By identifying your pages through relevant keyword links you are "telling" the search engine which keywords the linked pages represent. The rule applies for both internal and external anchor text."
2，怎样写链接文字
1) Make it easily understood by the user. Be honest about the anchor text. What it says is what you should get.
2) Important link positioning top left to bottom right. (throwing tons of links at bottom helps little).
3) Exact anchors that best support the content on the link to page. Its great to use tons of links where the anchor text suggest importance to "web design" however if the page is specific to "web development" then the use of "web design" link anchors will be less effective.
4) The use of "broad" has the benefit of aiding "broadly" e.g. using links to a website about "college degrees" where the link indicates "degrees" has the benefit of gaining associate degrees, bachelor degrees, masters degrees, as well as the specific subject matter for the degree itself link computer science degrees.
A link anchor however about "masters degrees" dilutes the value to other degrees e.g. bachelor degrees - so it is a game of tradeoffs.
5) If attempting to do item #4 for "web" to capture "web design", "website design", "web development", "website development", a text link anchor looks quite inappropriate. Thus the value of image links e.g.
Code:
<a title="web" href=""><img alt="Web" src="web.gif"></a>
where the broad term is less apparent and the image actually reads "web design".
3, 争取外部链接时，反向链接文字用相同的还是不同的？
-问题： I have been reading conflicting advice regarding link building. Some sources claim that you have to use the same anchor text all the time, while others claim that G may penalize you for doing so. Can anyone comment on this?