I don’t collect or save any information about visitors to my website, except to the extent that various of the tools or services that I use do so.

The ones that I’m aware of are:

• WordPress — The blogging tool that I use as a content management system allows users to create accounts for the purpose of making comments.  When users do so, it sends me email with the information that they’ve entered.  I usually save that email.  There’s probably also data kept in the database that holds the data for the site, which I can probably get at.  Over time I’ve used various statistics-gathering plugins, including StatPress and Jetpack to gather data about how many people view which pages and what links brought them here. Currently I use Akismet to filter spam. It probably gathers all kinds of information about visitors to my pages, and uses it to identify spam and spammers, but I don’t honestly know.
• Google Adsense — Some of my pages have Google ads on them.  Google no doubt keeps huge amounts of information about visitors to my pages.  I don’t have access to most of it, but I do get aggregate reports about how many times ads were served on my pages, and how many times someone clicked on an ad.  I don’t save any of that information, but Google does, and I go and look at from time to time.
• Dreamhost — This site is currently hosted on Dreamhost servers.  They keep server statistics that let me see things like how many visitors my pages have had, and save certain information reported by their browsers (such as what browser it was, and what the referring page was).  I don’t save any of that information, and I don’t know how long Dreamhost keeps the relevant log files.

The information is stored in various places and forms.  Some things, such as the statistics gathered by Dreamhost, are stored in databases belonging to and controlled by the service provider. Others, such as Google Adsense, use not only databases that are owned and used by the service provider for their own purposes, but also cookies stored on the computers of the people who visit my site.  Since I don’t really know what information is gathered or stored, I can’t make an informed statement about it.  Since the various services use the information for their own purposes, which I generally don’t have control over, I’m not in a position to promise that it won’t be misused.  Sorry.

The information gathered by the WordPress blogging tool is used in the obvious ways—for example, a comment that you enter is displayed on the system, together with the name and homepage link that you supply.  I might also use the fraction of the information that falls into my hands—for example, I might use the email address that you supply to contact you, if I think your comment is especially interesting.

Note that WordPress sometimes places cookies on your machine. It does this if you’re a logged-in user (on my site that’s usually just me). It does this if you leave a comment, storing the name, email address, and URL that you specify in the comment form so that the comment form can be pre-filled in for your next comment.

That’s about as much as I know about it.