Yahoo is using its developer conference, Open Hack Day 2008, to initiate a new property-wide social strategy, dubbed Yahoo Open Strategy (YOS).

Does this mean one more MySpace, Facebook, Friendster, Orkut, Twitter, FriendFeed, or Pownce (Ack!)? Probably. It means instead of developing one more site to go and see what your friends are up to, Yahoo is basically combining the entire Yahoo property into one gargantuan social networking site.

This means Yahoo’s previous attempts at a social network, namely 360 and Mash, had to be demolished. I suppose it doesn’t make sense to have a social network on top of a social network.

If Yahoo had its way, this will be the last social network you’ll have to sign up for. To prove it, Yahoo also released the Yahoo Application Platform (YAP) to give web developers the tool to create gadgets and sites on Yahoo properties as well as integrate Yahoo’s social platform on their own site as well. API’s and even a YML (Yahoo Markup Language) have been developed to enable access and sharing with Yahoo’s social network. As a partner in Google’s open-social gadget (or widget) platform, the application platform also integrates use of Google’s Open-Social API’s for usage on Yahoo properties.

Developers on the Yahoo campus this weekend are given the chance to get comfortable with, hack into the social network this weekend. Developers will be onhand to answer questions and hear suggestions. However, the tools will disappear on Monday to be released to the public at large “at a later date.”

No matter what side of the fence you fall on in regard to social networks, this might just be good news. Chances are, if you’ve ever used a Yahoo service, you already have a Yahoo profile. In fact, your friends are probably already on board too, which means practically no barrier to entry.

Under YOS, all remaining Yahoo properties (mail, messenger, maps, et al) are to be put under this over-arching social network over the next year — good news for developers itching to tap that gargantuan network.

It also gives Yahoo an altered identity. No longer is it a destination site to grab your data and go. It is now stretching its way to become a facebook-like destination — a way for people to stay and hang out with friends and do things like leave messages, poke and make zombies out of each other. You know, what social networks are for. That, my business-minded friends, is what they in the business call user lock-in.

The obligatory question is, are there privacy concerns? Yahoo’s new strategy is to open this information up to other developers and web users, but under a very thorough administrative process. When Yahoo’s applications, like Mail, MyYahoo, and even search are eventually ported under YOS, administration restrictions allow you to keep your personal information to yourself, share with your friends or share with everyone.

In other words, if you’re wary of sharing personal information with friends, you can opt not to at any time. Whether you’ve known it or not, we’ve seen exactly what this is going to look like with the recent BOSS and FireEagle releases — which are both currently incorporate how this service is going to work.

However, by having and using your new and improved sharable Yahoo profile, it means Yahoo has access to your data, which they promise to use only to improve future services and develop new applications. They also promise to use this information anonymously — third party applications will not have access to your data, unless you allow it.

That “unless you allow it” part is pretty interesting. Other social applications won’t allow third party access to your profile at all. In this way, Yahoo data is largely more open than other networks. For example, where other networks lock your data in, Yahoo has the potential to allow users to download their own data and maybe even convert it to another service in the future.