The NYT has a story on how hello became a widely used greeting. Turns out with Edison's help it beat ahoy as the standard phone greeting.
Unfortunately the article is not quite right, at least about the invention of the word. It was used earlier in the 19th century, at least back to 1834 to be exact.
What is neat is how telephones transcended the rigid etiquette of the time.
I think I'll have to start working in some ahoys now.