I've see lots of sites with links that will take you to the top of the page, but I've actually needed to use one. I've seen some sites where I can see ~7 of these links on the screen at once, whereas many have none. I can understand the intent, but they don't seem as valuable seeing as its so easy to get to the top of the page yourself. It seems like a waste to have site-specific ways to do something when there's a way that every user of any browser or operating system is already familiar with and skilled at.
question: Are these links useful enough to users to merit their appearance on webpages? If so, what are some general guidelines for their placement, appearance, and how many?