We are inundated with so many social streams that it is easy to forget where exactly we read something. For instance, there was a story earlier today on Twitter showing better clickthrough rates than Facebook. I know I saw it somewhere, but was it Twitter, Facebook, or in an email? It’s easy enough to search the open Web, but how do you search all of your personal information streams at once?

Introspectr, a personal search engine still in private beta, is part of a new class of startups trying to tackle this problem. (The first 100 people to click on this link will get an invite). You give Introspectr access to your Twitter, Facebook, and Gmail accounts, and it indexes them for you, along with the content of any email attachments or the underlying pages of any links. Then you can just search for any term and up come all the Tweets, emails, and Facebook messages where that might appear.

Another startup in this class is Greplin, which is a Y Combinator startup we’ve covered before. I’ve tried both. Neither one gets it exactly right, but they both point in the right direction. For instance, Greplin does not index the pages that people you follow are linking to. So unless the keyword you are searching for is in their Tweet, you are out of luck. But if someone Tweets, “Check this out” with a link to an article about clickthrough rates, Introspectr should be able to catch that.

Introspectr, however, doesn’t seem to update its index in realtime. You have to do that manually if you are searching for recent Tweets, or emails. And it doesn’t yet search your Facebook News feed, only your inbox messages. Doing a few random searches of words in my Twitter stream, Introspectr is hit or miss (for some reason Greplin isn’t showing me any Twitter results even though it shows that my Twitter account is supposedly indexed). When it finds the right Tweets or emails, it’s great. But this is really a feature Twitter should have. As part of Twitter search, you should be able to search only your own stream. And Google or Bing should add a similar type of social search functionality to their larger search engines. It’s such an obvious feature. But until they do that (which could be years), startups like Introspectr and Greplin are paving the way.

A new class of personal social search companies aare tackling thsi