During my year in Chicago as a YAV, there were a few times when I was called a "missionary" and each time I was extremely uncomfortable with that title.
It's not that I don't think missionaries are important and everything, but it's just that I think Christians tend to see Pastors and Missionaries as the only ones in "full-time ministry" and that bothers me - a lot. As followers of Jesus Christ, we are all charged with the command to love - even our enemies! Jesus doesn't require only a part of our life - not just on Sundays while we're at church, or on Tuesday nights at Bible Study, or when we feel like it - if you want to be a true follower of Jesus, you have to be willing to give Him every moment of your life, to strive to love everyone you meet with His love, to let the Spirit produce the fruits (love, joy, peace, patience, kindness, goodness, gentleness, faithfulness, self-control) in your life. And so we are all in "full-time ministry" - for all of our life.
My year as a YAV may have been more obviously about "serving God" but it was no more about serving God then the rest of my life. No matter what I end up doing next - if I wind up with that ever elusive "dream job" doing graphic design at a non-profit, or I continue building a photography business here in Oklahoma, or I get a job at Walmart - no matter what, I will be looking for ways to love the people I encounter and to make Jesus known.