Used to obfuscate links on forums and imageboards (such as 4chan) to either circumvent link blocking or to prevent the links from being indexed by search engines such as Google. Also helps deter lamers, bots and newfags from hoarding files from sites which have limited bandwidth.
The hxxp:// prefix is often used in hacked password lists for pornsites to help prevent them from being deactivated.
Also used to obfuscate links sent as NSFW (not safe for work) - so that you don't accidentally click on it and get into trouble. It gives you the need to copy it down and change it to "http".
To take something small, that doesn't quite qualify as a theft. Probably from the Danish "skæv" or the Dutch "scheef", both of which are pronounced similarly, meaning "askew, or not quite right'. To change an item's ownership without permission, but only something small and of little worth.
"I skeefed an apple off the neighbor's tree." "I skeefed some chips outta your bag when you looked away." "Don't skeef my chair when I go to the bathroom."