[kmfrk]

Atwood's new Discourse thingy recommends 1GB of RAM:

    We also recommend a minimum 1 Gb RAM to host Discourse,
    though it may work with slightly less.

~ http://www.discourse.org/faq/

Guess it depends.

[ptomato]

Note that that's their recommendation for a single VPS that includes the postgres & redis servers on it as well, not just the Rails stack.