Should former Marines who join another service give up the Title?

I do not understand the question. I am an Airman and a Soldier! You may not be able to serve two masters but you can serve one master two different ways. You carry the title Veteran either way just the same as I do. When people ask if I was ever in the Military I say yes the Army and the Air Force.

A resounding no.

Absolutely not. The title of Marine is one that is earned, and deserving or not, is one that is kept until death. I began my career in the Marines (4 active and 4 reserves, with 4 IRR), and I am ending it in the Army Reserves (10 years now). All that I am today was shaped by my experiences at MCRD San Diego, Camp Pendleton, 29 Palms, and Iraq. Those experiences helped to shape the kind of Soldier that I am, and have allowed me to be a better leader. I still to this day look back at my Marine training and gage what I am doing against that standard; not the Army standard, but the Marine Corps standard. It is a part of me today as much as it was when I graduated boot camp.

So, I respectfully say that it is not analogous to a woman taking a man's surname when getting married. She is who she is, regardless of the title that she carries. Marines are made in boot camp, and that makes the person that they are afterwards, regardless of the title... and the Marine title is earned.

Who cares? Be proud of where you've been and what you've done. I really dont care if anyone has been between multiple branches of military. A lot of people say, "oh this is way harder than [insert branch of service]." Truth is, most, if not none, can't even back that statement up. Now, for those who have been between branches of service, I have much respect for them. They been on both sides of the playing field. I'm not really going to listen to their stories of "hardship" and "struggle" that they had there, but still, I have much respect for them. It's the same for Officers who were once enlisted for at least their first contract. I have tremendous amount of respect for them. My Battle SFC Guillen was in the Marines over eight years ago before switching to the Army. I still, to this day, call him "Marine."

Once a Marine, always a Marine.

"Once A Marine Always A Marine" refers to Loyalty, Pride & Mind Set.
NO ! If an individual leaves the Corp and enters another branch of the military, they can be proud as hell that they were in the Marines but they are no longer Marines.. They are FORMER Marines...
To Me the statement applies to former Active Duty Marines who Leave The Marine Corps for Civilian Life or as Retired Marines.

No. Nuf said.

If that individual is no longer in the Corps, but serving with another branch, s/he loses the right to be called Marine. However, what i hope is s/he brings that USMC flavor to the gaining unit. I have the good fortune to have several former Marines in my unit and our overall performance outshines our sister companies by a country mile.

Understood that this was posted a year ago and from the perspective of the questioner, it is evident that the question is posted and self-answered. Being a Marine is an absolute identity regarless of the follow-on jobs, time in other branches and so forth. Ten years later my chest gets tight thinking about the clumsy words that I blurted when Senior Drill Instructor Eagle Globe and Anchor in my hand - I had an odd look on my face. "How do you feel right now?". I that I didn't feel worthy. I have alway been proud, but being a Marine is to be part of something more awesome than yourself. Semper Fi!

No,
if you earn the title of Marine, Keep it! Changing branches doesn't make you any less of a Marine