On how to choose a stack

In 2007 I left a growing 70 person startup to found my own venture. I was 26 and I knew everything I needed to know about web development and stacking chips. My stack choices were obvious:

Component | Choice | Regret ----------|--------|-------- Language | Ruby | N Web Framework | Merb | Y Database | Postgres | N Database | MongoDB | Y JS Framework | MooTools | Y Hosting Provider | SliceHost | Y