It's important to remember that for babies crying is their way of expressing themselves, whether it is that the are upset and miserable, frustrated, tired, uncomfortable, over whelmed or some other type of emotion. IMO it is important that babies do cry and do learn to express themselves and as parents we need to let them express themselves in a COMFORTED environment so that they learn to process their emotions independently. When we do everything we can to not let them cry, one can ask if we are teaching our children not to express themselves...
I don't want to start a heated debate here, but I just wanted to offer the flip side of this thought.....

Yes, babies cry to express themselves......to express a need for something. Which we, as parents, are required to give them. All those emotions you listed Missexcited are negative ones, and IMO they are all reasons to comfort a baby, to STOP him or her from crying. Babies learn to express themselves in other ways too, more positive ways like smiling, laughing and cooing. So crying is not their only form of communication - just the one that they use to tell us that something is not right in their world. It can be something as simple as them being tired, but whatever it is, they are not happy about it. And that is why I feel a pull in my tummy, even as I type this, and I could never leave my babies (or any babies) to cry. JMHO.