Having a slow modem is also a plus when... "dubious" sites attempt to lock you in by opening multiple new windows every time you attempt to close a browser window or leave their site.
If you have a fast connection, the newly opened windows will load their content very fast. These new pages will have the same "onunload()" methods embedded within them, further trapping you in a multitude of open browser windows.
If you've got a slow connection, you've got time to close the windows before the pages load.
Um, like, this happened to someone else surfing free porn sites. And they told me about it. Yeah, that's what happened.