Agent Oriented Design in the real world?

The use of the term "agents" in AI (which is most likely what you're referring to, it's the most common academic reference) is really a synonym for "software program that acts on a user's behalf". An agent is seen is more attractive because it's a somewhat personified term, being a proxy for a user; also, it tends to be associated with higher order functionality (planning for agents, learning for agents, autonomous agents, etc.). More about the origin of the term on Wikipedia:

http://en.wikipedia.org/wiki/Software_agent

Given that, the term "agent" is more about the purpose and type of software, not how it is programmed. OOP has more to do with how it is technically designed/implemented.

So there is nothing wrong with designing your agents using OOP principles. The two subjects are not mutually exclusive.

Also, keep in mind (as some of the comments above allude to, and I agree with): use of "agents" in academia is more romanticized term; most software acts on some user(s) behalf, and so there is agent functionality in many things. It's just software at the end of the day, and if you removed the term "agent" from our collective lexicon, you wouldn't be punishing the capability of pure software design/implementation any. You will see elements of this same debate in forums specifically about agent oriented programming, e.g.:

http://ootips.org/agent-orientation.html