As also pointed out by Richard Stallman: "of course, to be really sure which key is mine, you need to get my key fingerprint from me or follow a chain of signatures. If a phony key appears to be signed by someone you trust, you should see what's up with that person."
Additionally, if you want to send me encrypted messages or recieve encrypted responses, you must send me your key since I will not use a key server to retrieve it. I do not promise to keep it permanently if we do not talk often either.