Google tends to pull out all stops when it comes to security of its products and services, which is why they started enforcing new rules for Chrome extensions last year on Windows based machines for users who ran the Chrome browser. Once upon a time users could grab Chrome extensions from various other places on the net besides the Chrome Web Store, but after the rule change Google made it clear users would only be able to download and install Chrome extensions that were available in the Chrome Web Store to better prevent extensions with risky, hidden software from being installed.
This was a decent change for Chrome users as it meant there would be less of a chance of installing any malware although it was and still is a practice only happening on Windows computers for those who are using the regular version of Chrome. Google will be changing this in the coming months however, and will be extending this policy for Chrome extensions to Mac computers as well as Windows machines that are using a Dev Channel version of the Chrome browser. What does Google hope to achieve by expanding this extension policy? The same results that they've seen with the initial change from last year. According to Google's Chromium blog post of the announcement about bringing this extension change to Mac users and Dev Channel users on Windows, they state that after enforcing the requirement that extensions be hosted on the Chrome Web Store, they saw a 75% decrease in customer support help requests to remove (uninstall) unwanted Chrome extensions. Those are the type of results they likely want to see shift to the groups of other Chrome users.
Google will be making these changes to the Mac version of Chrome starting in July while they'll begin to enforce the changes on the Windows Chrome Dev channels starting today. The reason for the fast track for Dev Channel users Google says, is due to malicious software that has been forcing users to access Chrome in the Dev Channel so unwanted extensions could be installed. With a word to extension developers, Google states that they'll continue to support local extension installs during the development stages as well as installs via their Enterprise Policy.