The tech industry is full of battles – epic and otherwise – between companies that position themselves (or are positioned by others, perhaps) as enemies: Apple versus Microsoft. Google versus Microsoft.

Having a target like this isn’t a bad idea, as it helps you make sure you can differentiate yourself from your competition. But startups are sometimes advised to not take on these sorts of skirmishes, at least not explicitly, particularly with more established corporations. Compete for users, don’t pick a fight with Google, suggests a recent LA Times article.

But taking on your challengers directly shows a great deal of confidence and guts. And if you have the product or service to back it up, you can demonstrate vision and ambition – and attract the attention and admiration of users and investors.

Posterous may be the example of the week for this.

On Monday, Posterous announced that it would be posting one resource a day for the next two weeks to help users migrate their content from “dying platforms” to the microblogging service. “A lot of you have asked for help moving your old blog, photos or videos to Posterous. You grouched about dying platforms that haven’t added new features in ages, sites that have made it too complex to perform the most basic tasks and places that smother your content in ads.”

Posterous’s first target: Ning, whose abandonment of the freemium pricing model back in April frustrated a lot of users. Next target: Tumblr, the site that Posterous is probably most frequently compared with. You might be hard-pressed to call either Ning or Tumblr “dying platforms.” Or if you’re Posterous, you might not be.

Posterous is clearly calling out and openly taking on its competition.

In a blog post earlier this week, Flightcaster co-founder Jason Freedman wrote about the three characteristics he sees in the YC companies that are successfully raising money: Leverage, Product and Ambition.

YC alum Posterous is demonstrating that ambition – “pure, unbridled ambition” – hoping to show it has not just the guts, but the product to back that up.

How its competition responds over the course of the next two weeks will be interesting to watch.

Photo credit: Flickr user REL Waldman