In order for a platform to be viable, it’s got to appeal to more than just the design or tech communities. It’s pretty easy to forget this.

It’s pretty easy to pander to markets that are already hooked into the internet more than they should be; it’s pretty easy to just write blog posts or tweets engineered to snap up the attention of those you’ve met in the tech industry and who subsequently follow you on Twitter, on Facebook or on Tumblr. But when someone manages to snap up both the attention of the tech industry and everyone else, that’s when you’ve got something big. This is why Posterous is currently trailing behind Tumblr in growth and in popularity.

A lot of people have a lot to say on the subject. Posterous’ controversial and massively aggressive marketing campaign back in 2010 somewhat ridiculously called WordPress, Tumblr and a few other platforms out-dated and dying. In July of 2010, VP of Marketing at Posterous, Rich Pearson, told ReadWriteWeb, “It’s too early to gauge the long term [success of the campaign], but in the short term, it’s been huge.” While it may have been successful in the short term (and the shit storm that ensued sure did cause a lot of ruckus), it’s tough to say that anyone is still thinking about the whole spectacle.

You’ve probably heard that Tumblr recently took in a huge amount of money from VC giant, Sequoia Capital. They also grabbed a new product director from the New York Times, Derek Gottfrid. It’s been a pretty turbulent six months for Tumblr– there’s been horribly frequent downtime and their API has been basically unusable for extended periods of time. They’ve been as bad as (or perhaps worse) than Twitter was in the early days (no one misses the fail whale, no one).

But through all of the turbulence, Tumblr has been incredibly good at stoking their community fire. Every week they promote a new batch of up-and-coming artists, personalities and musicians on their staff blog. Their dedication to controversial political events, such as the recent popular movements in Egypt and Lybia, is totally refreshing. Even their error pages contain a reference to supporting the survivors of the recent events in Japan.

It’s tough to say the same thing for Posterous. Their official blog looks like it’s more concerned with business and business practices than it is with art, design and popular political movements. While Tumblr seems to be rapidly gaining users, over at Posterous, it still looks like it’s business as usual. Yes, Posterous has the technology, but both their marketing tactics and their seemingly hands off approach suggest that they don’t have the spirit to appeal beyond the somewhat insular tech community.

The numbers don’t lie: there’s only one micro-blogging platform getting out of here alive, and that’s Tumblr.