I would not use blog entries from 4 years ago as representative of the way things are today in the world of programming and technology.
Memory requirements will be a bit higher on some stacks than others. Remember that Discourse, as we say many times on http://www.discourse.org is built for the next decade of the Internet. We’re 1 year into a 10 year plan. We want to make decisions that might seem aggressive now, but are still smart 5 years from now. Maybe even prescient!
That said, memory is cheap and getting cheaper every day. For example in 2009 our Stack Overflow web tier servers had 8GB RAM. The ones we built for Discourse in late 2012 had 32GB RAM (and dual 512gb SSDs). That is a 4x increase in 4 years.