OK, sounds like we need to draw a line here. Friendly competition will help each other out and still maintain a profit or a favor owed. Friendly competition will not try to poach your clients even though they know who your clients are. If my client goes to my competition, than so be it - BUT - I would expect my friendly competition to inform me. However, if my competition knowingly goes after my client, than that's a whole different story and the party is over. For example, A couple months ago I met a guy that I know is a client of my friendly competition (Mike). We chatted about products and services and I gave him my card. I said - Here's my card, don't call me. Call Mike first, if he can't help you out, let me know and I'll take care of you. I quickly sent Mike an email telling him what happened. In no way, shape or form did I try to poach his client. Mike was happy about my honesty and we can both sleep better knowing that we can trust each other and continue to thrive of each others success in the future.
I try to keep track of who is who and who has what. IE, Guy down the street has a cnc router, the other guy has an 8' printer, the other guy does screen printing, the other guy does wraps, etc, etc, etc. All I need to do is keep track of it all and use it to my advantage. I let everyone know that "THIS" is what I do. Now that I know what they can do, I can use that to my advantage by selling their product. Buy from them at trade pricing, add a mark up and sell to my happy client.
Maybe there's something you can do that the competition can't. Maybe you can do it cheaper than they can. Figure it out and make it work for you.
Best way to beat the competition is to turn them into a client.
After all, there's nothing wrong with a little friendly competition...