While I never bitch at people stealing kills since I don't really care (I'm in it for the credits only - the less work I have to do to get those credits the better...
), it is theoritcally possible for a well organized team to get more XP by distributing kills across all players (due to the bonuses you get for reaching specific thresholds for weapon kills, skill kills, and assists) rather than one player getting the majority of the kills. Once a player gets the gold medals for kills, weapon kills, and skill kills - theoritically, it is better for other players to pick up the kills at that point to also get their gold medals and add to the total overall shared bonus.
However, in order to do this and make it really worth it in any meaningful way, you have to really be on top of things. Additionally, it's not like the bonus XP makes it even that much more worth it anyway (compared to the effort) though - so anyone really wanting to crunch the numbers that seriously (because of the distribution factor) are a bit too hardcore for my liking.