We have an undocumented API to obtain the data that makes up the charts page, if you're interested, PM me and I can show you how it works.
As for an API to any private account data. We don't have such a feature right now, but I could create that if there is enough demand.
Right now it is possible to use what our game client does in its update script, but you'd have to authenticate with user/pass and then use a session cookie.
Thanks! What I'm looking for right now is (my own) private account data. I'm trying to write a script that logs my investment data from various sites over time so I can visualize it later. No big deal for now, but please count my vote for an API to access account data in the future.