I hosted my WP blog for free on OpenShift and (with free Cloudflare) it was able to handle Reddit/HN traffic spikes without a problem. Not sure why everyone doesn't do something similar.
cache, cache, cache... Reddit and HN do not really send a lot of traffic... It baffles me to see peoples sites go down for 20k+ unique visitors total for the day... I've seen basic Wordpress installs with a few tweaks such as caching in place handle hundreds of thousands of unique visitors a day every day for months... It's not rocket science..