The mobile gaming platform wars continue to heat up, as we just learned this morning that publisher PlayPhone has acquired mobile social marketing company SocialHour in a $51.5 million deal. VentureBeat is reporting that the stock-only purchase means that no money has changed hands, but PlayPhone now has the marketing partner they believe they need to make a splash in the online gaming space.

The primary reason for the acquisition of SocialHour is raising the profile of PlayPhone and coming up with various ways to cross-promote the games within its network. This will likely be achieved through a variety incentivized and non-incentivized promotions for PlayPhone users.

What sets PlayPhone apart from the competition is its ability to unify players across a variety of platforms. Anyone signing into the PlayPhone network can play with anyone else who’s also online regardless of what type of device they’re using. Finally, iPhone and Android owners can play together. just as the great digital gods intended.

The acquisition is a bold move for PlayPhone as they fight to carve out a niche in the mobile social gaming world. Larger, more established competitors like GREE/Openfeint and DeNA/Ngmoco already have a major head start in the arena, though it’s still a young enough industry that a clever upstart could jump in and shake things up. PlayPhone currently boasts roughly 3 million subscribers, and now that they have a marketing firm under their purview that number is set to grow tremendously.