meh i agree with the OP. i come from a textpattern/drupal background where the core downloaded files are barely half a meg, let alone 100+ megs unzipped.
if you have a good core product, then having authors maintaining their plugins overall should not be an issue.
reasons why you would want a small core? single example would be what if a built-in feature doesn’t work the way you want it to work and you find a suitable plugin instead? now you will have to deal with that ‘built-in feature’ code loading alongside your plugin creating unnecessary overhead. i’ve already come across numerous comments on various forums saying magento is trying to do too much at once.
though i do understand varien/magento is aiming towards a ‘corporate/enterprise’ image so any potential feature sets considered ‘bloat’ (not saying there is, as i haven’t really dug into magento too much yet) by your everyday small/medium sized businesses may not look like such to larger, high-end companies who may also not be using whatever features but just enjoy having ‘a bunch of stuff.’
either way, such aforementioned reasons are why i generally prefer to use textpattern over cms’s like expression engine (not to mention its proprietary nature) overall. i love EE, but textpattern with its stripped core and feature-by-plugin architecture RUNS CIRCLES around EE in terms of space, resources, etc etc on any server you throw them on.