A few months ago I registered at www.eve-kill.net because when you kill someone, unless you are the person to execute the final blow, you don't get the kill mail for it. Since then, my CEO has mentioned that he doesn't want anyone registered on any sites like that because it provides too much intel for any enemies looking to cause us harm. They can see where we hang out, what type of ships we typically fly, what those ships are fit with, and who we typically fly with.
For those reasons I completely understand not wanting to be registered. I've learned that PvP comes down to a few things that ultimately decide who will win and who will lose. The #1 thing I've learned is preparedness. Whoever is more prepared will greatly increase their chance for survival. This is part of what makes up a good FC. A fleet commander that knows the names of all the other ships out there, how they are typically fit, and the best tactics for bringing them down, will easily beat a fleet twice his size if the other fleet is just a ragtag group thrown together hoping to win by sheer numbers. If a FC is outnumbered 10 to 1, chances are they are going to retreat, not because they're scared, becaues there is no point in everyone dying, just to be stubborn. Unless of course they actually believe they can beat a fleet ten times their size with proper ships and tactics.
All that said, a small portion of why I engage in PvP is for the kill mail. I don't need to be the one that gets the final blow, but as long as the kill goes to a member of our corporation so it ends up giving us credit, then that's all that matters to me. But since I commonly find myself in mixed fleets, that's not always the case. I have to wait 30 minutes after killing someone and hope that either the person that got the final blow or the person that blew up, was registered as well, otherwise there is no record that I have had a hand in their demise.
Right now, our corporation is working on its PvP kills to try and join another branch of our alliance that specializes in PvP. We aren't allowed to join until we have proven ourselves with kill mails. They don't want spies and noobs that can cause huge headaches to infiltrate their group, and I respect that. But that brings me back to whether or not I keep my API key registered or remove it to prevent enemies from harnessing intel on our fleet makeup.
I fight for fun, but without the kill mail there is no proof. Which in turns ends up resulting in people making up kills that never happened, just to look cool. Maybe they should add a new category in the combat log for Assists. That way, kill mails stay protected but even logi pilots can start to see the fruit of their labor. They can receive credit if they are involved with healing someone that got an assist or got a kill. Right now, being a logi or support pilot doesn't receive any recognition, and I think it's time they start to get some well deserved love.