Social networking website Facebook yet again succeeded in angering a large section of its 900 million privacy-conscious users over the weekend when it surreptitiously switched many of their profile e-mail addresses with a domain address.

Many users who had e-mail addresses from Gmail, Yahoo or Hotmail, would have discovered on Monday that their profile now showed a address instead. While the option to revert to the external e-mail address exists, it requires tweaking of their profile information display settings. Users also have the option to hide the address.

However, with the majority of users receiving no clear warning about the change, Facebook drew the wrath of tech bloggers and ordinary subscribers who complained bitterly that the changes echoed Facebook’s ham-handed approach to enforcing such major changes every now and then.

CNN quoted tech blogger Gervase Markham, said to be one of the first to draw attention to the change, as saying, “Facebook silently inserted themselves into the path of formerly-direct unencrypted communications from people who want to email me.” Arguing that this was known as a “Man in the Middle Attack,” in the context of electronic hacking Mr. Markham asked, “What on earth do they think they are playing at?”

As on earlier occasions, Facebook appeared to have been caught off-guard by the scathing criticism. Meredith Chin, Facebook’s manager of product communications, was quoted as saying, “We basically defaulted to show your Facebook address as we rolled this out, just to keep it consistent for everyone... It’s an additional visibility setting.”

Its critics slammed the switch as an attempt to resuscitate Facebook's e-mail system, which was announced in late 2010 but never really took off. Forbes magazine captured users’ mood in a simple headline “Facebook’s lame attempt to force its email service on you.”

Some estimates suggest that India ranks third in terms of the size of its Facebook user base, with over 46 million members. The company’s first ever Initial Public Offering last month was widely regarded as a disaster, after its share price dropped from $38 to around $28, wiping off around $4 billion from the net worth of its founder, Mark Zuckerberg.