Google (Nasdaq: GOOG) is getting serious about social search, just as Twitter is remaking itself into a discovery tool.

In simpler terms: It's on, baby.

First, on Tuesday, Twitter teased a richer version of its website. New features include embedded media (no need to click a link to see a photo), mini-profiles (click a username to pop up more information in a sidebar), and most important of all, related content. Click a tweet, and Twitter will tell you about other things you might be interested in.

Related content is why both Facebook and Google have tried to buy Twitter. They knew this day was coming.

Facebook has been preparing for it by transforming itself into a platform for e-commerce. Google, for its part, has launched Buzz and added social features to services such as YouTube. But now The Big G wants to go further.

In reports published by The Wall Street Journal and Reuters last night, CEO Eric Schmidt said Google is on track to add in "layers" of social networking to its various properties. The company is also working on a Facebook killer it refers to internally as "Google Me," the Journal reports.

We'll have to wait for Google to show us what this all means. Regardless, it's an important step that's reflective of salesforce.com's (NYSE: CRM) successful Chatter interface. Apple (Nasdaq: AAPL), too, has taken an application-specific approach to social networking with iTunes Ping.

I'd like to see Google use Gmail as its default social client, with Google Me aggregating streams of information as an inbox "view." I'd also like to be able to quickly act on content that appears in Google Me using mail or Talk.

For example, say I find a Fool.com story I'd like to share with a select number of friends. In Google Me, I'd open a mail message or IM to a custom Google Me address and choose who to send to -- in this case, just a group in Google Contacts.

Google Me could also be like social network aggregator Ping.fm, allowing users to update all their Google services at once -- everything from Aardvark to YouTube. Schmidt's "layers" comment suggests this is a possibility.

Would either of these innovations put Twitter and Facebook on the defensive? I think so, but what's your take?. Weigh in on the social search debate using the comments box below.