Does anyone know if a BalloonCallout can be used for labeling or is it restricted to annotations only?
Yes, as far as I know you can. You should be able to get the label properties from IGeoFeatureLayer.AnnotationProperties. QI over to ILabelEngineLayerProperties and you can set the symbol used for labeling. When you create the symbol, use a formatted text symbol. The callout can be applied by setting the IFormattedTextSymbol.Background property.
Does ESRI actually have people on staff that can write applications using their API?
Yes, they do. All of the ArcGIS Desktop applications are written using the ArcObjects API. In fact, that's the reason the ArcObjects API was created.
Wouldn't it be nice if there was a place you could request samples?
Nice, yes. Practical, no. ESRI provides a pretty good amount of free support for developers already. You can purchase technical support through a support agreement/contract, although I don't know that you can simply pay them to write a sample. I think you actually have to have a problem.
Wouldn't it be nice if someone at the company followed these forums?
They do. Technically these are user forums, meaning users provide all of the participation. However, there are a handful of ESRI employees who regularly post here.