On Twitter, URL shorteners have become vastly important. With the 140 character constraints for each tweet, we wouldn't have the freedom to share a link and explain its significance without them. It turns out, not URL shorteners are created equal, either.\n\nA new report from Pingdom assessed the nine most popular URL shorteners on the Web. These services exist as their own websites where you can shorten a URL manually (such as TinyURL), or are embedded in other applications, like TweetDeck. Overall, Pingdom crowned Bit.ly and Ow.ly as the most reliable in terms of uptime. \n\nOw.ly displayed an annual downtime of zero hours. Bit.ly came in second with an estimated 1.8 hours. The popular TinyURL, which was one of the first such services to hit the market, experiences about 3.5 hours manually, the report says.\n\nCIO.com looked at Bit.ly with particular interest; the majority of our tweeted links on @cioonline use the service to make sure our readers connect with our new stories as the post to the Twitter stream. We were pleased to hear that the service's "99.98% uptime is the equivalent of failing once for every 5,000 click." \n\n\nSome argue much is at stake as it concerns short URLs, and I tend to agree. For one, we have become reliant on them to communicate on Twitter. If they flake out, it's possible people could miss some valuable information. Secondly, they serve as a catalyst for spam, since we can't see what's behind the link before we click on it (without a cumbersome "preview" process, which most people don't use). One critic, Joshua Schachter, contends that all the re-directions caused by these services will make our experience on the Web more sluggish. As a result, we might need to develop a streamlined way to cope with the problem. \n\nThese services also serve more purposes than shortening links, however. Many tout analytics tools that allow you to measure how many people click on the link \u2014 a helpful feature for marketers and media people. \n\nThe stability of these companies will matter a great deal moving forward. If one of them goes out of business tomorrow and people searched for the links it shortened on Twitter, that could be a big problem. We'll be watching these services as they try to build sustainable business models. Or for better solutions altogether. \n\nC.G. Lynch covers consumer web and social technologies for CIO.com. He writes frequently on Twitter, Facebook and Google. You can follow him on Twitter: @cglynch.