When Google bought YouTube in 2006 for $1.65 billion, there was a lot of speculation as to how the search brand would leverage its new popular, if volatile, property. Would Google be named as part of copyright suits?

By 2008, YouTube’s developing ad endeavors translated to $200 million in revenue. By 2010, the video portal was live-streaming athletic events and serving around 2 billion videos a day. It was, for all practical purposes, the world’s most popular on-demand TV network — and the second biggest search engine on the planet, after its parent. In October, YouTube co-founder Chad Hurley stepped down as CEO to recast himself as a Silicon Valley haberdasher, and one of Google’s earliest employees, Salar Kamangar, assumed the top spot.

Now, it looks like Google is making another move to bring the YouTube brand further under the Google umbrella — and just like Facebook’s new default profile page, it’s irking users who don’t want to connect all the dots.[more]

YouTube account holders may be surprised to find the above message, which locks them out of their accounts when they try to sign in until they linked to to a Google account. Don’t have a Google account? Sign up for one.

In 2008 Google heavily promoted linking arms with YouTube as a option. In 2009, new YouTube accounts were automatically linked to Google in the creation process. Now, those with older Youtube accounts will longer have an option. As the new lock-out page reads, “You will no longer be able to sign in to Youtube without a Google account.” The only other available option to linking accoutns is to sign out of Youtube.

Currently, Twitter users are tweeting their displeasure with the policy.

A few weeks ago, the behind the scenes tightening of the Google-YouTube integration could be seen when users discovered they could not delete their YT accounts. At the time, YouTube reps said that this was a “bug,” but that “if you created your account after May 2009, you should be able to delete your account by deleting your whole Google Account.”

Will users rebel? Some might but so many more will probably just click the link button. Though, those blighly clikcing may want to consider this warning from Youtube in Oct.:

“Please note: If you link your YouTube Account to a Gmail Account you will not be able to change the email account with which your YouTube Account is associated/linked in the future. When you link a YouTube Account to a Gmail Account the Accounts are permanently linked and this cannot be undone.

If you link your YouTube Account to any other type of email account, you can choose to link to a different Google Account later.”

But the account linking blip comes in the wake of the site’s redesigned user homepage, and coincides with the (very weak and largely unknown) movement to boycott YouTube today in protest of the website’s increasing commercialization.

Given the pushback (and ire raised by Facebook’s user profile tactics), Google might be wise to keep in mind the current tenderness of many users.