My wife recently replaced the soap dish in our kitchen (and the soap on it) with a liquid soap dispenser. Within about a week, we've used about half the bottle of liquid soap, whereas solid bars of soap would tend to last a month or two.
Clearly the liquid soap is going to be far more expensive (unless we find a very cheap supply of it), but I'm interested in comparing other whole-of-life impacts that the two options have.
Let's assume the liquid soap doesn't contain the common anti-bacterial agent "triclosan" (which has it's own set of problems).
Does one biodegrade better, or have a lower embodied energy, etc.