Drink The Kool Aid

From the JargonFile:

    When someone who should know better succumbs to marketing influences and actually begins to believe 
    the propaganda being dished out by a vendor, they are said to have drunk the Kool-Aid. Usually the 
    decortication process is slow and almost unnoticeable until one day the victim emerges as a True 
    Believer and begins spreading the faith himself. 

    The term originates in the suicide of 914 followers of Jim Jones's People's Temple cult in Guyana in 
    1978 (there are also resonances with Ken Kesey's Electric Kool-Aid Acid Tests from the 1960s).

Can also refer to vendor lock-in. For example, Exchange Server comes with a big pitcher of Microsoft Kool-Aid.

Examples of use:

  "They drank the XML Kool-Aid."