Client

Client
1. Precompile templates wit Grun or someting else
2. Don't do any logic/view creation inside of router
3. Use stylus for CSS (express middleware or precompile with grunt)
4. Don't put raw HTML in your JS, only in templates
5. No functions in your backbone event's hash, use string of method name instead
6. You might find .toJSON() gives you more flexibility when rendering templates vs model.atributes
7. Put fadeout/fadein times as some option variable somewhere so you dont have constants hardcoded in your JS

Server
1. Rename shit so it makes sense (db->models/schemas, routes/controller.js -> config/routes.js, routes/ -> controllers/)
2. Could use MongoDB 2.4 beta feature full text search if you need to find people by email/name/etc
3. Chat-roulette style matching, or friendslist click to join (green LED if already online)