Posterous, the “dead simple place to post everything“, has won a lot of praise for building an easy-to-use publishing platform. And it’s so confident that users of other platforms will like it that it recently launched a campaign that is enabling users of other platforms to migrate their content over to Posterous.

Tomorrow, Posterous will set its sights on perhaps the juiciest target in the blogosphere: WordPress. WordPress, of course, is the popular open source blogging platform/content management system. And WordPress.com, which is the hosted solution offered by WordPress parent Automattic, hosts millions of blogs.

Will Posterous be able to lure away a sizable number of WordPress users with a WordPress import tool. Or is its entire effort really a fruitless attempt at being all things to all people?

Unfortunately for Posterous, it seems the latter is more likely. The reason: as cool as it is, it’s going to be difficult to build a business by poaching users who are willing to flee a variety of other platforms, some of which aren’t even in the same space as Posterous.

When Ning dumped ‘free and asked its users to pay up or get out, for instance, Posterous welcomed them with open arms by offering a Ning migration tool. But there was just one problem: Ning provides a service for creating full-blown social networks; Posterous is essentially a blogging platform. So Ning users really couldn’t move their social networks over to Posterous; they could only move over their Ning blogs, which represented a small fraction of their content on Ning.

In targeting WordPress, Posterous is at least going after users of a ‘blogging‘ platform, but it remains to be seen just how compelling Posterous’ offer is. Some non-paying WordPress.com users looking for an even ‘simpler‘ solution might have an interest, but users of WordPress who host their own installations probably won’t be impressed. After all, WordPress 3.0 is compelling as a true CMS, and for bloggers/publishers looking to build something unique, it would be hard to ditch WordPress for Posterous given that WordPress is almost infinitely extensible through a robust theming system and plugin API.

To be sure, a subset of the users of all platforms Posterous is targeting will never make use of all of the features these platforms offer. For these kinds of users, a switch to Posterous may be viable. But the problem here is that these users are probably of questionable value to Posterous as a business. That may seem harsh, or even elitist, but one only need to look at Ning to recognize that building up a network of small-time publishers who don’t pay you anything is a tough strategy to succeed with. It’s far easier to create and extract value from a platform’s power users, yet Posterous seems to think that it can do okay by getting other platforms’ ‘weakest hands‘ to fold.

At the end of the day, one might argue that Posterous has little to lose by trying to poach users from other platforms. That may not be the case given that these are unlikely to be profitable users, but regardless of that, in trying to be all things to all people, Posterous probably has little to gain too.

Photo credit: Robert Sanzalone via Flickr.