The process of Search Engine Optimization (SEO) has many different associated tasks, as many of us know. The subject of linking has been discussed in great detail on many forums and blogs, and the importance of using keywords within anchor text (a somewhat simplified but fairly accurate definition) is unquestionable.
As people (read here: SEO's and SEO-"tinkerers") try to increase the amounts of inlinks to their website using keyword-rich anchor text, questions have been raised as to "how much is to much?" The current consensus seems to be that you should vary your anchor text when actively linking to particular pages. So-called "natural links" (ones that you do not solicit) will naturally [:)] have varied anchor text.
A thread was started at High Rankings Forum the other day which details an email a member received that requested that he go back and vary the anchor text he was using to link to the person's site. The thread, titled "Google Penalizing For Links?, What's your thoughts...." describes someone asking:
...I'd greatly appreciate it if, the next time you are updating your site, you could tweak your links to me so that they express what you think about my site in your own words...
OK, so this may seem a little tinfoil-hattish, and the site owner is risking losing the links completely, in my opinion. Also, I feel like Jill Whalen that there is no penalty for repetitive anchor text, just a possible devaluing of some of the links. Unless the site you are asking to change your anchor text is owned by a friend, I probably wouldn't recommend it. The answer is to instead focus on using varied anchor text in future link building efforts.
See the comments and the interesting spin off discussion on relevancy at High Rankings Forums.