Be careful what you are measuring. Most home broadband connections are asymmetrical, meaning that the data rate is higher from the internet to your home PC (inbound) than from your home to the internet (outbound). My UK ADSL line is about 2Mbps inbound, but about 400kbps outbound.
If your site is popular and offers large downloads/pictures/videos etc, then your site could easily suffer slow download speeds with a few simultaneous visitors.
Couldn't agree more. Do you really want hackers getting access to all files on your hard drive? All that personal information you've got there? It could happen. If your site is just HTML then you are probably OK. If you start running scripts (your own or other peoples) then you should start to worry seriously about security.