When you don't own your own site or your data, you are dependent on that silo to keep your personal data safe. If you add sensitive data such as credit card numbers, personal details or messages, or log into your account through a password, you must trust that your data is stored securely and will not be compromised. Site Deaths and Site Changes are other reasons why you should own your own identity and content on the web.
This page is a chronology of content hosting sites that have been compromised by a 3rd party.
- Disqus: In October 2017, the blog commenting service Disqus announced they'd suffered a data breach.
- 2014-01 Snapchat In January 2014 just one week after Gibson Security detailed vulnerabilities in the service, Snapchat had 4.6 million usernames and phone number exposed.
- 2014-02-15 Kickstarter hacked, user data stolen 
- In a blog post, Kickstarter staff mentioned that "No credit card data of any kind was accessed by hackers. There is no evidence of unauthorized activity of any kind on all but two Kickstarter user accounts" and that "Actual passwords were not revealed, however it is possible for a malicious person with enough computing power to guess and crack an encrypted password, particularly a weak or obvious one." 
- Recommended action: Users urged to create a new password for Kickstarter accounts and other accounts where password was used.
- Bitly: In May 2014, the link management company announced they'd suffered a data breach.
- Tumblr: In early 2013, Tumblr suffered a data breach which resulted in the exposure of over 65 million accounts. 
- Last.fm: In March 2012, the music website Last.fm was hacked and 43 million user accounts were exposed.
- Dropbox: In mid-2012, Dropbox suffered a data breach which exposed the stored credentials of tens of millions of their customers.
Sites or tools offering services to know about hacks:
- Why - other problems with using and depending on 3rd party sites
- Google Graveyard (on pinterest.com)