for one, see the reply from the handle cryptonector further up

> Inheriting from a class creates dispatch problems, and there's instance variables/fields/whatever to deal with. Never mind multiple inheritance, as that gets hairy real fast. With interfaces there is no hierarchy, and all there is is a type and a data, and you either pass them around together, you monomorphize to avoid the need to pass two pointers instead of one, or you have the data point to its type in a generic way. With class hierarchies you have to have operations to cast data up and down the hierarchy, meaning trade one dispatch table for another.

I agree with all of this. With interfaces, you get all the benefits, but none of the downsides.