Earlier this week, Greplin announced it had raised a new $4 million from Sequoia Capital, and revealed that it might open up to the public this week. Now it has. Until now, it has been in closed beta, and now everyone can see what it's all about.
While not perfect, Greplin has some interesting things going for it (you have to pay if you want to access larger amounts of data). There's no question that Greplin could be an even more useful service if it was simply integrated with regular search results, similar to how Google already displays its own social results. I previously suggested that Google (or another company - like Microsoft) might look to acquire Greplin, but I think much of what Greplin does, Google could achieve on its own.
As I said, Google could certainly sprinkle in the results from across its own services (Gmail, Docs, Reader, Buzz, etc.), and with the recent acquisition of fflick, could just as easily sprinkle in the Twitter element (though without the Facebook element, the results could never be as good as they could be otherwise).
With content farms aiming to greatly expand, it seems that it will only become increasingly hard for Google to keep a variety of sources among its top results for any given query when a few select brands are pumping out so much content. Google has indicated it's looking to solve the content farm problem algorithmically, as opposed to the human-edited style of Blekko, which recently banned 20 of the top content farm sites, though Google has released a Chrome extension geared toward crowdsourcing search quality to some (probably minor) extent.
Google needs to get social search right to be the most effective it can be. Unfortunately without Facebook data, it doesn't seem like it will ever be able to truly give users the best social results, as Facebook is clearly the dominant social network with about 600 million users. For many people, the majority of their online social behavior happens in Facebook. Their real friends are on Facebook, so if they want to search for a topic, and have any mentions of said topic from their actual friends, Facebook data is important.
This makes Greplin useful for some types of queries. With Greplin, you can search across your Facebook, Twitter, LinkedIn, and Gmail connections, along with feeds you've subscribed to in Google Reader, your own Google Docs, your own Google Calendar, etc. More services are said to be coming soon.