by Stephen Shankland
July 6, 2009 4:00 AM PDT

Twitter's dramatic rise has helped ignite an industry to shorten Web addresses to fit within 140-character messages. With the technology, though, comes a new handful of challenges. Among the challenges are reliably connecting people to the Web sites they want to reach, keeping spam and phishing attacks at bay, and maintaining the service into the future.

Joshua Schacter, founder of Yahoo's Delicious site for storing and sharing Web bookmarks and now a Google programmer, summarized the issues in an April rant about short-URL problems. "I feel that shorteners are bad for the ecosystem as a whole," he concluded. Until a remote future arrives when Twitter and the telecommunications industry decide 140-character messages are too short, though, URL-shortening services aren't going to go away.

Fortunately, their potential problems can mitigated through careful use, and newer services such as Bit.ly are being designed expressly to avoid the pitfalls. And even if some service falls by the wayside and stops functioning--well, welcome to the real world, where not all information is preserved. "In the digital age, everything has a certain amount of bitrot," said Paul V. Mockapetris, who invented the Domain Name System (DNS) that serves as the Internet's address book.

URL-shortening services are abundant and becoming more so. They're usually designed with a priority on minimum character length, not easy reading: Is.gd, Bit.ly, Twurl.nl, Tr.im, Sn.im", Cligs, and TinyURL. If you want to see dozens more, Mashable has a long list. And the traffic they handle is large. On a typical day right now, Bit.ly is used to create 5 million to 7 million shortened URLs each day, and it handles 25 million requests to expand them--and the growth rate is at a breakneck 5 percent to 15 percent week over week, the company said.