Why not? Look at Yuri's profile. He's got several employees who take care of different stages along the assembly line. Each photo goes through a process from one person to the next. I see a lot of similarities there to a factory/assembly line. Not to say that he's not creative or anything but he's certainly turned his work into an industrial process

OK, I admit it, I've been a lurker: I've been here for several months and this is my first post 

OK, so I'm with iS, SS, DT, and Ft. Though admittedly I don't upload much to Dreamstime or Fotolia anymore. I make about 60% of my microstock income from iStock, 30% from Shutterstock, and the rest from the other two. At iStock I am about to reach Silver and am considering going exclusive. I've done some calculations, using theoretical future earnings, and have found that at the Silver level exclusivity earnings would counter the loss of income from the other sites. The benefits for me are less time uploading, better licensing options, and the eventual possibility of working for Getty.

However, I could also go the route of joining more agencies. This would also produce increased earnings, but would also require much more time uploading and keywording. How do you get around this? I know some photographers hire assistants to do the keywording, what about the rest?

I am going to assume that most of the folks here are NOT exclusive anywhere (as if they were, they'd be over at their agencies forums and not here). What would really help in this ageold query is a rough percentile breakdown, like this:
Number of agencies you belong to - Name1 x%, name2 y%, name3 z%, etc. As I see it, with enough data, we could all benefit from seeing whether belonging to many agencies or going exclusive might be better than sitting on the fence with only a few agencies.

So, for me: 4 - IS 60%, SS 35%, DT 3%, FT 2%