CNet on the Twitter-inspired rise of URL-shortening services:

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. Snipurl has delivered 53 billion since its inception. And TinyURL has a database of 293 million URLs.

These services sprung up in the early oughts to prevent long URL strings from being broken in e-mail marketing. They’ve mushroomed with the popularity of Twitter and the the 140 character message limit.

The business of these services is found in the “analytics” feature that can report how many clicks happened when and where and what Web page they lead to. They sell ads, too. The problem is reliability:

[E]ven 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.

Our biggest problem? Spam!

SNVC asks, “Are you an affiliate marketer looking to cloak your affiliate links?…If you choose to check the ‘Hide Real URL?’ box then it will allow you to keep your shortened URL in the address bar by using a hidden-frame trick.”

But avoiding the issues of opaque links is top of mind for many services. For example, adding the word “preview” in front of a TinyURL link will show a Web page with the destination URL expanded. Greasemonkey scripts and extensions let some browsers automatically show the expanded link. And Bit.ly’s API permits the Tweetdeck application to automatically show the ultimate destination.

The once and still favorite among tech types, bit.ly, is now the market leader. It was recently selected as Twitter’s shortener of choice and has a new set of Digg-like products in the works, called bit.ly Now:

Bit.ly’s new Bit.ly Now service will show popular links at any given time, just like Digg (for now, Bit.ly sends the most popular link every hour to a twitter account). When Bit.ly Now launches, that link data will be combined with additional metadata about the URLs. In particular, they plan to extract important entities, people and topics from the stories in real time, allowing for a categorized approach to popular links. Bit.ly says they are talking to a number of third party services, including Reuter’s Open Calais, to help them do this.

Finally, from the what-won’t-they-think-up-next department, GCut.to:

The service (launched anonymously) allows you to create a shortcut link that will go to the first result for a particular Google search — the same result that the “I’m Feeling Lucky” button on Google takes you to.