Anchor text, that text that is highlighted when you go to follow that link, is not really important. Just the fact that you got a backlink is all that matters. Wrong! Choose quality before quantity to get ahead. Links from like-themed sites are worth much more than a link from something totally unrelated.

This makes sense if you think of it from the user perspective. If you were on a car site, wouldn't you be more likely to follow a link to a fellow car site than a cooking site. This is exactly the point that Google is trying to get across. Search engines are trying to provide the user with the best and most relevant information in the search results pages.

Google tracks all your backlink anchor texts as part of their evaluation. Having a lot of links with all the same text appears like a form of spam to Google so you will only get credit for part of those backlinks.

Google bases this whole anchor text assumption based on natural linking. If you did nothing link-based and just built a good site, people will link eventually. It is very unlikely, however, that the anchor text they all use to reference you would be the same. This is the stance Google takes which is why varying your link text is beyond important.

Don't get me wrong, just having the backlinks helps a ton, but varying those keywords takes that gain you get from all the work to the next level.

Here are some good tips for anchor text:
1.Don't? use the URL of the site (yoursite.com) as the anchor text. This does you no good as there is no correlation with keywords or the like.
2.Figure out your target keywords and use varying combinations of them. Google picks up on this and you get a great bonus for varying your anchor texts. For example, if the keywords you might use are ?link exchange?, try also using ?exchange links? or ?find link partners? or ?exchange links with other webmasters?. This appears much more natural. Many times it can make all the difference.
3.Don't use the same link text everywhere because it will look unnatural and you lose some of the great parts of backlinks.

WWGD (What Would Google Do) is a way to look at how to attack things like link exchange campaigns. By appearing more natural you appeal more to what Google is attempting to do so you are much more safe from future updates like the Jagger update. Just follow the 3 easy tips I put above and you're well on the way to ever-increasing site rank and link popularity.