Once upon a time, there were three prominent microblogging platforms, Twitter, Plurk and Jaiku. One became incredibly popular, one introduced a side-on view, and one was acquired and then released by the Google Fairy Godmother.

Others fell by the wayside, including Pownce, and Rejaw.

But how do they compare now, after the mainstream adoption of Twitter:

Obviously this doesn’t tell the complete story, as it tracks web visits only, but it’s safe to assume it’s proportionally correct. Twitter’s close to 25 million Unique Visitors, Plurk is holding steady between 250,000-300,000 for the past year, and Jaiku has dropped from 70,000 down to 30-40,000 for the last two months measured.

In fact, it’s not even winning the Open Source Microblogging Platform war – as Identi.ca has grown slightly while Jaiku declined.

Meanwhile, Google has listed the 46 official accounts it has on Twitter.

And in the meantime, we’ve seen the rise of Twitter clients such as Tweetdeck, internal microblogging such as Yammer,  the blend of micro and macro blogging in Tumblr and Posterous, and video and audio blogging with the likes of 12 seconds and Audioboo. Not forgetting the lifestreaming element of the likes of Friendfeed.

And although we talk about forums, blogs and Web 2.0 social networks as if they’ve reached the endpoint of their evolution, there’s still a lot more to come from them – I’d say the social elements of the web aren’t even 15% of what they’ll become in the next 10 years.

The question is how you as a person, you as a company, or you as a developer can find clarity through it all…

(There is also the question fo what Google were thinking re: Jaiku, and how it’s managing to miss out on the rise of Open Source as much as it did on the rise of microblogging – after all, the platform itself doesn’t appear to be the cause)