I recently came to think about the serfs... Well, it all started when I looked at Space Marine Codex and found out a description of a Adeptus Astartes Destroyer which had the personnel capacity of 5 Marines and 150 Serfs. Now a ship of this size would be a perfect base of operations for a player-character strike team of 5 (or so) Marines.
Now, the other thing that really struck me there was the cheer amount of serfs aboard. Not that I didn't expect marines to have a huge population of serfs around (I actually pretty much expected there would be at least 20+ serfs for each full marine), but it actually got me thinking... The vast majority of any chapters population is composed of personnel who are not marines. Thus it makes sense that even though majority of the activities is aimed at keeping the 1000 (or less) borthers in fighting shape and gear the actual society of the chapter is serf-society. Its not like the marines even have much time to be around the fortresses and ships since they are urgently and constantly needed where serfs don't wander (in effect, in combat). So basically everything else except the actual tip-of-the-spear fighting is in the hand s of the serfs inducted to chapter cult.
Now, what I want to hear is your vision on serfs and bondsmen in marine chapters?
How they view the marines and how the marines see them?
How closely the serfs work with marines in day-to-day work?
How closely do they associate in the chapter-society?