A timeline of Google's messaging rivalry with Facebook. Original inspiration from source [23], enhanced and corrected from [33]:

- 2006-02-07: Google Talk integration inside Gmail goes live [35]

- 2006-09-26: Facebook opens up to everyone (not just colleges) [36]

- 2007-02-14: (corrected date) Gmail opens up to everyone (not just invite-only) [37]

- 2008-04-06: Facebook chat goes live [34]

- 2008-07-11: iOS App Store launches [38]

- 2008-08-26: Facebook hits 100 million active users [24]

- 2008-09-23: Android 1.0 launches [39]

- 2008-11-11: Google Talk introduces voice and video calling [40]

- 2009-03-11: Google buys GrandCentral, launches Google Voice [1]

- 2009-04-08: Facebook hits 200 million active users [25]

- 2009-06: iOS gets push notifications [42]

- 2009-06-25: Google Voice invitations being serviced [2]

- 2009-09-15: Facebook hits 300 million active users [26]

- 2010-02-04: Facebook hits 400 million active users [27]

- 2010-05-20: Android gets push notifications [41]

- 2010-06-21: FaceTime released with iOS 4 [43]

- 2010-06-22: Google Voice opens up invite-free to everyone in the US [3]

- 2010-07-21: Facebook hits 500 million active users [28]

- 2011-01-05: Facebook hits 600 million active users [29]

- 2011-05-30: Facebook probably hits around 700 million active users [30]

- 2011-06-28: Google+ launches, with text chat "+Messenger" and video chat "+Hangouts" [4]

- 2011-07-06: Facebook introduces video calling powered by Skype behind-the-scenes, needs installation [5]

- 2011-08-09: Facebook introduces Messenger app [6]

- 2011-09-22: Facebook hits 800 million active users [31]

- 2011-10-12: iMessage released with iOS 5

- 2012-04-23: Facebook hits 900 million active users [32]

- 2012-09-20: Facebook tries SMS sending from Messenger [7]

- 2013-04-17: Wired editorial on "Will Google Hang Up on Voice?" [8]

- 2013-05-15: Google launches 'Google Hangouts', which subsumes Google Talk, Google+ Messenger, Google+ Hangouts [9]

- 2013-10-29: Facebook discontinues send-SMS support in Messenger, sends Messenger message instead [10]

- 2013-10-29: Google Hangouts Android App gets SMS handler support [11]

- 2014-02-19: Facebook announces it will acquire WhatsApp [12]

- 2014-04-09: Facebook removes chat from its main app, forces people to use Messenger [13]

- 2014-09-11: Google Hangouts gets Google Voice integration [14]

- 2015-03-25: Facebook announces Messenger Platform for business, bot, and ad integration [15]

- 2015-04-27: Facebook Messenger gets native video calling [16]

- 2016-01-27: Hangouts 7.0 asks users to use Google Messenger for SMS instead [17]

- 2016-06-14: Facebook Messenger gets Android SMS handler support [18]

- 2016-07-13: Hangouts 11.0 removes support for merged conversations [19]

- 2016-08-16: Google releases Duo [20]

- 2016-09-21: Google releases Allo [21]

- 2016-10-07: Duo is replacing Hangouts in the base Android install [22]

- 2017-01-23: Google launches rebooted Google Voice app, with Hangouts-like UI

[1] https://googleblog.blogspot.com/2009/03/here-comes-google-vo...
[2] https://googleblog.blogspot.com/2009/06/google-voice-invites...
[3] http://googlevoiceblog.blogspot.com/2010/06/google-voice-for...
[4] https://googleblog.blogspot.com/2011/06/introducing-google-p...
[5] https://www.facebook.com/notes/philip-su/building-video-call...
[6] https://newsroom.fb.com/news/2011/08/a-faster-way-to-message...
[7] https://techcrunch.com/2012/09/20/facebook-android-update-yo...
[8] https://www.wired.com/2013/04/google-voice-future-uncertain/
[9] http://www.theverge.com/2013/5/15/4318830/inside-hangouts-go...
[10] https://techcrunch.com/2013/10/29/facebook-messenger-phone-n...
[11] http://arstechnica.com/gadgets/2014/09/google-hangouts-gets-...
[12] http://newsroom.fb.com/news/2014/02/facebook-to-acquire-what...
[13] https://techcrunch.com/2014/04/09/facebook-messenger-or-the-...
[14] http://arstechnica.com/gadgets/2014/09/google-hangouts-gets-...
[15] https://developers.facebook.com/blog/post/2015/03/25/introdu...
[16] http://newsroom.fb.com/news/2015/04/introducing-video-callin...
[17] http://arstechnica.com/gadgets/2016/01/google-hangouts-7-0-f...
[18] https://techcrunch.com/2016/06/14/facebook-messenger-texting...
[19] http://arstechnica.com/gadgets/2016/07/google-hangouts-for-a...
[20] https://blog.google/products/duo/meet-google-duo-simple-1-to...
[21] https://blog.google/products/allo/google-allo-smarter-messag...
[22] http://www.theverge.com/2016/10/7/13202866/google-hangouts-a...
[23] http://www.whoishostingthis.com/blog/2014/10/22/instant-mess...
[24] https://www.facebook.com/notes/facebook/our-first-100-millio...
[25] https://www.facebook.com/notes/facebook/200-million-strong/7...
[26] https://www.facebook.com/notes/facebook/300-million-and-on/1...
[27] http://web.archive.org/web/20100212075226/http://blog.facebo...
[28] https://www.theguardian.com/technology/2010/jul/21/facebook-...
[29] http://www.businessinsider.com/facebook-has-more-than-600-mi...
[30] http://www.adweek.com/news/technology/facebook-nears-700-mil...
[31] http://mashable.com/2011/09/22/facebook-800-million-users/
[32] http://money.cnn.com/2012/04/23/technology/facebook-q1/
[33] https://news.ycombinator.com/item?id=11114518
[34] https://www.facebook.com/notes/facebook/facebook-chat-now-we...
[35] https://googleblog.blogspot.com/2006/02/chat-email-crazy-del...
[36] https://techcrunch.com/2006/09/26/facebook-just-launched-ope...
[37] https://googleblog.blogspot.com/2007/02/from-gmail-with-3.ht...
[38] http://www.apple.com/pr/library/2008/06/09Apple-Introduces-t...
[39] https://android-developers.googleblog.com/2008/09/announcing...
[40] https://gmail.googleblog.com/2008/11/say-hello-to-gmail-voic...
[41] https://blog.serverdensity.com/android-push-notifications-tu...
[42] https://www.urbanairship.com/push-notifications-explained
[43] https://web.archive.org/web/20100609163523/http://www.engadg...