Hi
One other thing worth bearing in mind. If the user accesses the internet via a Proxy server, then any address you can get will contain the Proxy's IP address. If this is the case, there is no way to get the users 'real' IP address, as with DHCP address their IP will change all the time. And hence you would never really know who bookmarked your site.
You could create a small form for them to enter their info into and then bookbark the page. But remember people get frustrated with things like this so most would bypass and manually bookmark anyway.