If I understand your re-worded question correctly, then the answer is no. You only have control over information that is stored on your computer or on your own website. Any data about you on someone else's site can only be erased by them.
For instance, if I do an advanced search in the Cnet forums, and type in the username motownbob, or simply click on your username, I'll be able to see a list of all posts you've made here at Cnet, and click on each one to see what you and others said. That information is stored on Cnet's servers, and can only be erased by them. You have the ability to contact a moderator or administrator and request that the post be removed, but beyond that it's out of your hands.
Another example: If I do a general web search through Yahoo of my username (mousearoma), I receive a list of 498 matches:
* A good portion of the matches are for my posts here on Cnet. By having a moderator remove my post, the result should no longer come up in the search.
* A lot of the matches are advertising and ''junk'' sites which copied content from Cnet onto their site to attract more visitors to their site. The deletion of my original post may or may not remove the excerpts from their sites, and search matches, depending on how they have their site set up.
* There are also a few matches for the username ''mousearoma'' from other forums, and one Geocities page, most of which are not mine. Those I have no control over, but it shouldn't/doesn't matter since it's not my information/postings.
* If there were matches concerning someone speaking about me, I could ask the webmaster of that site to remove the comments if warrented, but the decision is up to the webmaster unless said comments violated the law.
Hope this helps,