The incident happened yesterday, and the Metamask team says Google provided no prior warning of explanation for their actions.
PSA: MetaMask has been delisted from the Chrome Web Store. We are unsure of why this is the case and we will update everyone as we get more information. All other browsers are unaffected.— MetaMask (@metamask_io) July 25, 2018
Google did eventually restore the extension a few hours later, but not after it received intense criticism online, on sites such as Reddit or Twitter.
The @metamask_io currently listed in the @googlechrome app store is a fake, phishing app. Do NOT download. The real MetaMask extension has been removed this morning without explanation. Follow @metamask_io for updates. pic.twitter.com/4CPS3wfFqE— Augur (@AugurProject) July 25, 2018
This is incredible. Google removed the real @metamask_io from their Web Store, leaving behind a fake one which uses official branding. Play Store also has a fake MetaMask, which uses a known phishing address. What are you doing, Google!? pic.twitter.com/C7dnVndpX3— Sampson (@jonathansampson) July 25, 2018
If you use @metamask_io in Brave, you are unaffected by the Chrome Web Store removal of the MetaMask extension. Brave maintains its own extension server to protect users from several scenarios, including abruptly-deleted extensions. https://t.co/IG9OKeAZwM— Brave Software (@brave) July 25, 2018
Google also removed the clone Metamask extension, which used Metamask name and branding to promote itself.
According to Jonathan Sampson, a developer for the Brave browser, that extension appears to have been malicious, as it used an email address that was previously used in phishing operations.
Many suggested that incident might have happened after Google's staff tried to ban the clone, but banned the original extension instead. Google didn't provide a follow-up explanation to the Metamask team following the incident.
PSA2: We are back on the chrome webstore. Stay tuned for a formal retrospective from the team.— MetaMask (@metamask_io) July 25, 2018
Metamask is a new type of application that implements the new Ethereum decentralized apps (DApps) concept that lets developers build apps that can interact with the Ethereum platform directly, without having to run an Ethereum node through which to funnel operations.
DApps is how the Opera and Brave development teams have added built-in Ethereum wallets to their browsers.