Captain Obvious...has arrived!
Copy a number from a site to send to a friend who doesnt have an iphone and cant look up the number!
This is not about copying from A SITE. Copying a number from a site has always been possible in 3.0. The post you are replying to (and failing) was about why would you want to copy a number from the CONTACTS and paste it in the keypad field.
My personal guess is that let's say you would like to add some code or edit it for some reason before dialing. Anyway, more options is a good thing.