I agree that as a practical matter it does what you want a majority of the time but generic collections let you mandate that an author has thought about equalit

I agree that as a practical matter it does what you want a majority of the time but generic collections let you mandate that an author has thought about equality for his object at least a little by implementing IEquatable. Particularly since a default definition of equality doesn't always make sense (as in the case of the fs). As with the case of explicitly sealed/unsealed classes, it seems like Jon's MO is to make programmers think about some of these things more carefully rather than have a "correct 90% of the time" default; a sentiment which I can definitely appreciate. :) Anyway, he discusses it at approximately the 36 minute mark. Well worth a look.