Twitter's signed a deal with UK-based analytics form Datasift allowing it to sell the content of tweets going back over the last two years.
Datasift says that almost a thousand companies have already signed up to access the Twitter Historics data, which they'll use for marketing purposes.
"The sheer volume of data being produced by Twitter represents a huge challenge for companies trying to extract insights from past events," says DataSift CEO Rob Bailey.
"Historics solves this problem, providing businesses with a platform to intelligently filter and extract meaning from two years' Twitter data."
Every tweet, says Datasift, is 'enriched' with details including sentiment, topics, web-links, location and social media influence. Those who buy the data, it says, can analyze trends in customer conversations and identify market influencers.
"With Historics we've democratized and simplified how businesses can unlock insights from billions of social conversations," says Datasift founder and CTO Nick Halstead.
Datasift's obviously very pleased with the deal, and for Twitter it means one more source of cash. Users, though, might not be so happy.
"If you aren't comfortable with firms being able to mine your past tweets - and potentially gather information about you - you may wish to delete your old postings and think more carefully about what you share publicly on the internet in future," says Graham Cluley on the Sophos blog.
"Furthermore, if you haven't already done so, you may also wish to change your Twitter account settings to prevent the site from sharing your physical location when you post a tweet. Twitter offers the ability to delete location information from tweets you have made in the past."