In December 2013, Apple acquired for just over $ 200 million, according to the Wall Street Journal The Topsy Labs, a company specialized in analysis and search tweets.
Yesterday, two years later, the service was permanently shut down by Apple and this was announced (see s) by Twitter itself:
We've searched our last tweet.
– Topsy (@Topsy) December 16, 2015
Topsy.com now redirects to a company support article that explains how to search iGadgets.
Apple was probably not interested in what Topsy offered in practice with this acquisition, but in the technologies developed by it and in expertise of your team that went to work in Cupertino.