Feature creep is generally a result of poor management or a bad idea, in which nobody had the balls to say "no" to either the bad design in the first place, or to the guy who wanted to add the features (which can be as often one of the people building it as one of the people paying for it).
Feature creep has made its way into the public arena as mission creep, to describe a political or military adventure that has gone out of control in the same way, for the same reasons.
Generally the product of optimistic programmers or overambitious managers, feature creep is generally considered a bad thing. Feature creep makes a program that would have done one thing well into a program that does ten things, all poorly. Microsoft Outlook suffers badly from feature creep.
Him: We need to make sure it has a standard SNMP interface. And metrics analysis.
Me: Watch out for feature creep - it's only a screen saver.
Customer: "Good point. I'd better add 'easy to use' to the list."
Feature creap can prolong a release date with infinate delay. see Vaporware
This is often caused by managers or consultants that do not have a clear view of what product development entails and start sentences with "How easy would it be to..."