In internet marketing, if you sell a lot, you are bound to have at least 1 unhappy customer. Worse, you are bound to have 1 really unhappy and spiteful customer. These guys will post all over the web saying how you suck.
With any luck, you can go to that guy, explain the situation, try to reason, and have that info taken down. So now the info or the entire page is down, but Google is still bashing your name, because of search results and old cache data. Now what?You could simply wait until Google re-indexes the page, but that can seem like an eternity if you are waiting for it to happen. Search results can stay in the cache for months. (Which was a good thing when my one site was hacked and this was the only way to get the data back).
With that page, you enter the URL of the page (not the google cache page), select either that the webmaster has blocked the page, and confirm it shows a 404 redirect, or that the content has changed and you simply want to recache the url.
After you put in the correct information, Google will get to it and re-cache or delete the page from Google search results. Voila! Your problems are done quicker than if you just waited for them to re index the page.
PS. this also works if you just changed your website and want Google to reflect the new changes quicker. An all too common scenario is accidentally getting confidential info indexed, and you need it removed fast.