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heatseeker: n.

[IBM] A customer who can be relied upon to buy, without fail, the latest version of an existing product (not quite the same as a member of the lunatic fringe). A 1993 example of a heatseeker was someone who, owning a 286 PC and Windows 3.0, went out and bought Windows 3.1 (which offers no worthwhile benefits unless you have a 386). If all customers were heatseekers, vast amounts of money could be made by just fixing some of the bugs in each release (n) and selling it to them as release (n+1). Microsoft in fact seems to have mastered this technique.