Someone who does what's called "Link Surfing" or "Link Riding". The action of clicking on links within webpages. One might begin on twitter, follow a link to youtube, click on a link in the sidebar to a news website, and go from there to another site. By the end of an hour, and Link Rider will usually have about eight windows open from different websites.
"What's been taking Bob so long? I thought he was just checking his email."
"Oh... Wendy sent him a link to a Wikipedia article. He's probably been sucked into all the pretty blue links."
"Great! He's probably going to be on there for hours!"
"What a pathetic link rider..."