Is an unencrypted wallet secure if bitcoind is not accepting RPC calls? I'm interested in setting up a P2Pool node (which requires running bitcoind) to run a little mining pool for myself. Before you ask, nope I'm not even trying to break even, I know I'll lose money on this. Just want to play around and get a feel for how these things work.

My question is: I hear over and over again that it's important to take security precautions with bitcoind and wallets, but I've had trouble teasing out exactly what those security precautions are. If I have bitcoind not accepting RPC calls (as is the default), is there any danger to using the out-of-the-box unencrypted wallet?

If the information helps, I'll probably run the node in EC2, and have a cron job that frequently transfers any bitcoins earned through mining into an account in an exchange so I can play around with that side of things as well (so I'm not worried about large sums of bitcoin building up in my bitcoind wallet).
Turning off RPC will prevent that particular attack vector, but if the coins are on a machine connected to the internet, that's a lot of vulnerabilities and attack vectors to consider.

That said, if you're running a node on EC2, you're not going to generate enough bitcoins to be worth stealing. If the point is to figure out how everything works, I wouldn't worry about the bitcoins you'll be mining since it'll be so little (at most $10 per year).