The microblogging service Twitter debuted five years ago, and by all accounts it's one of the great success stories of the social media era.

Twitter boasts 200 million users and 350 billion tweets per day, and it's a ubiquitous reference on mainstream TV. Visit Twitter today, and it's a hive of frenetic activity. Millions of people rely on the service for news, commentary, blog updates and social interaction. Twitter is about to close an $800 million funding round, which values the company at about $8 billion.

Suddenly, however, the service has been rendered obsolete by Google's new Google+ service, and also by the company's failure to capitalize on its five-year window of opportunity to innovate its way to indispensability.

It's only a matter of time before Twitter becomes a ghost town. Here's why.

Twitter's Google+ problem

Google launched its Google+ social site about three weeks ago. The site's perfect storm of social features will sink Twitter.

Google+ has Twitter-like "following," rather than Facebook-like "friending." That means you can follow anyone without his or her permission. Google+ has a Twitter-like "feed" or "stream" that presents the posts of the people you follow the moment they're posted.

Asymmetric following and instant feeds are two of the four core attributes of Twitter. The third is brevity. Twitter famously restricts posts to 140 characters or less. And the fourth is an API that enables other companies to tap into the stream and do interesting things with the flow of tweets.

But it's only a matter of time before Google+ will have all four of Twitter's core attributes.

Many Twitter users like short tweets or, more accurately, they like the fact that blabbermouths are forced to be concise. The resulting stream is terse, and skimmable, although many of the best tweets actually link to blogs or articles that are longer and wordier. (Never mind that the reason for the limit was initially to fit the tweets into SMS text messages, a requirement made obsolete by the use of mobile apps.)

The coming APIs from Google will enable third-party companies to present Google+ streams in Twitter-like summaries, with links to full posts. Anyone who likes the shortness of Twitter posts can also get short Google+ posts. Even without those APIs, people are already doing this. Silicon Valley entrepreneur, blogger and venture capitalist Guy Kawasaki, for example, has already built a page he calls "Pluserati," which presents short versions of the most recent five posts by the biggest users on Google+. By hovering your mouse pointer over the short version, you get a longer version. By clicking, you get the original post.

While Google+ will soon do all the things Twitter does, Twitter can't support a long list of the things Google+ supports. Conversations, for example. Each post on Google+ can be followed by comments where users can hold a detailed and satisfying conversation about the post. On Twitter, commenting is awkward because when you comment, your comments are not generally seen by the poster's other followers, but by your own followers, who probably did not see the post. You see a lot of replies on Twitter referencing posts you never saw. For a social service, Twitter is pretty antisocial.

Also on Google+, you can post pictures and videos directly in posts, launch immediately into a video chat, send your posts to nonmembers and even present all your posts marked "Public" as a blog available to anyone with an Internet connection.