When visiting BlueMix a link should be provided that informs the user of the various services being employed, their functionality and purpose, and what information, if any, they are collecting and intended use.
While most people do not notice these multiple service being employed or the setting of cookies, a small minority, including me, does find the practice to be both common across many Web properties, as well as dismaying due to lack of disclosure.
To experience for yourself, install NoScript add-on for Firefox and set Firefox preferences for third-party cookies to "Ask every time" and then load up bluemix.net.
NOTICE TO EU RESIDENTS: per EU Data Protection Policy, if you wish to remove your personal information from the IBM ideas portal, please login to the ideas portal using your previously registered information then change your email to "email@example.com" and first name to "anonymous" and last name to "anonymous". This will ensure that IBM will not send any emails to you about all idea submissions