Following brief stabs at porting titles to the iPhone and other devices in in past years, most top social game developers have by and large ignored mobile devices. Their reasons have been solid: the mobile social gaming market is by most accounts smaller than on Facebook, it can require significant changes to a web game, and it has very different customer dynamics.

But now we’re seeing signs that the biggest companies are becoming more interested in mobile again.

The clearest example is Zynga’s recent release of FarmVille on the iPhone. That seemed like an obvious move — Zynga is working hard to keep the FarmVille brand alive even as it ages on Facebook.

We recently received word, though, that the trend may go beyond FarmVille. Playdom, for instance, recently hired Steve Makofsky, a former Microsoft and Yahoo executive with deep experience in mobile, to become its new vice president of mobile platforms.

Like Zynga, Playdom has some older games on the iPhone, but has not made any big effort to put its newer games on any mobile platform. But hiring for a senior-level position suggests that there will be a substantial team working on mobile.

Zynga, also, is on the lookout for experienced mobile team members — both a product manager for mobile devices and a mobile user interface designer.

It’s unlikely that most Facebook game developers will move quickly toward mobile. However, it looks like the largest companies are at least thinking hard about how to at least integrate mobile development in the future.

Their platforms aren’t proven to work as well as social networks in terms of of social games’ focus on user-to-user communication and the virtual goods business model. But overall, the opportunities are looking better than ever have before. The iPhone continues to lead, now with the iPad device and iPhone 4 firmware that broadens the types of games that developers can build for the operating system. Android, meanwhile, continues to see device sales increase, even though app success stories are few and far between. Other companies, like Microsoft, RIM and Nokia, are also busy trying to improve their own developer platforms. It makes sense that as competitors in the mobile industry improve their platforms, social game companies are preparing to take better advantage of all of their efforts.