I think that map projections are poorly understood and oddly implemented. They're too often political statements, and people bashing mercator are looking for a 'new default' to adopt without thinking about the subject in depth.
And our computers understand them by codes, like
EPSG:900913, stifling the
instinct to experiment with them or invent new ones. The projections you have
'to choose from' are limited by the big list of projections
your computer understands,
and those you can bet on other computers having.
Project it Yourself is a first step towards an alternative system, where we create projections, understand their implementations and ramifications, and treat them as part of creating maps, rather than a setting that's ignored.
It's not about 'adding more projections' or 'replacing proj4'. While I really like kartograph, I don't think that snark about projection choices is productive, or that just adding more options is the future. It's a negative trend to talk about the tradeoffs of a projection like spherical mercator without understanding the inherent balance between distortions. This is the discourse because we don't implement projections, but we treat them like they've always existed. The idea that projections are choices is broken.
↬ spatialreference.org for making this mess more navigable