Wrong conclusion. There's a difference between bad idea and bad execution.
MailChimp is a business site. Twitter and Facebook are personal mediums. There's a mismatch. As a manager, I wouldn't want my employees using personal mediums for business (I have no control), and conversely, as an employee, I don't want to be logged into Facebook from work, or share my Facebook information with businesses. I would never log in to MailChimp with either of those.
On the other hand, we use Google Apps for Business. I use that as a common login for everything that supports it. Most businesses use Google for business in some form (if nothing else, Google Docs or Youtube or similar), so even if not Google Apps, there's already some integration.
Single sign-on is much more secure than either managing 100 different passwords, or having 100 different businesses managing my password. It's much more convenient. It's just a clear win.
MailChimp is a business site. Twitter and Facebook are personal mediums. There's a mismatch. As a manager, I wouldn't want my employees using personal mediums for business (I have no control), and conversely, as an employee, I don't want to be logged into Facebook from work, or share my Facebook information with businesses. I would never log in to MailChimp with either of those.
On the other hand, we use Google Apps for Business. I use that as a common login for everything that supports it. Most businesses use Google for business in some form (if nothing else, Google Docs or Youtube or similar), so even if not Google Apps, there's already some integration.
Single sign-on is much more secure than either managing 100 different passwords, or having 100 different businesses managing my password. It's much more convenient. It's just a clear win.