Is it crazy to not rely on a caching system like memcached nowadays ( for dynamic sites )?
If your site performance is fine then there's no reason to add caching.  Lots of sites can get by without any cache at all, or by moving to a file-system based cache.  It's only the super high traffic sites that need memcached.
What's "crazy" is code architecture (or a lack of architecture) that makes adding caching in latter difficult.
I was just reviewing one of my client's applications which uses some old outdated php framework that doesn't rely on caching at all and is pretty much completely database dependent.
I figure I'll just rewrite it from scratch because it's really outdated and in this rewrite I want to implement a caching system. It'd be nice if I could get a few pointers if anyone has done this prior.

Rewrite will be done in either PHP or Python
Would be nice if I could profile before and after this implementation
I have my own server so I'm not restricted by shared hosting