Google's Realtime Search has been mysteriously missing since earlier this week, Search Engine Land reports. The option on the left sidebar is now unavailable, and a direct visit to google.com/realtime returns a 404 as shown above. Google offered two explanations. It cites Google+ on the first one:

We’ve temporarily disabled google.com/realtime. We’re exploring how to incorporate our recently launched Google+ project into this functionality going forward, so stay tuned.

And Twitter on the second one, which seems to be the main reason:

Since October of 2009, we have had an agreement with Twitter to include their updates in our search results through a special feed, and that agreement expired on July 2. While we will not have access to this special feed from Twitter, information on Twitter that’s publicly available to our crawlers will still be searchable and discoverable on Google.

It's no secret that Google and Facebook don't get along too well. Since Google has limited access to Facebook's data, Twitter became the main pillar of Google Realtime Search for the past two years. That being said, it's puzzling why Google did not reach a new agreement with Twitter. Google told Search Engine Land: "As for other features such as social search, they will continue to exist, though without Twitter data from the special feed." When relaunched, Google Realtime Search will include contents from Google+ and other social networks. We will see if by then Twitter will be back on the list, whether through a renewed agreement or a smart algorithm that nicely sorts public tweets. Source: Search Engine Land