I'm wondering here....
HOw does that work for non exlcusives? Does the limit increases with time?

MY upload limit is set at 24/168

I wish they give you a per year limit, instead of a week limit.

So at this upload limit rate, if I wanted to increase my portfolio, I would only be able to upload 1248 this year.

illustrators have 24, why is that? when a photographer needs to have 2500 sales to get there..

1248 is a large number.  Unless you are an image factory, 24/week is a lot to produce, week in, week out, for a whole year.  Try it.  You'll see what I mean.  And as you move up the canister level system, you will get more upload slots.  The highest amount of slots for a non-exclusive is 40/week for black diamond.  

The other way to get more upload slots is to go exclusive.  

Actually, somewhere I'll never be, but I have on good authority that when you reach 25,000 downloads you have 150 upload slots per week. Maybe it's just that person, but it was a question about uploads and exclusives and that's what he said. So there's your exclusive limit for anyone who cares.

I got a raise from 15 to 18 and didn't notice. I suppose I'd have to want to upload something to have paid attention? 

I don't know Luis...
My canister is silver, I'm only allowed to upload per week 24 of vectors, and 24 of photos..

Ah ok, your post didn�t expected you were silver, so the upload limits are equal

Current limits AFAIK are

Upload limits for non-exclusive contributors:

Base: 18
Bronze: 20
Silver: 24
Gold : 30
Diamond: 38
Black Diamond: 40

Upload limits for exclusive contributors:

Bronze: 60
Silver: 90
Gold: 120
Diamond: 150
Black Diamond: 200

as from last July.

See http://www.istockphoto.com/participate/contributor-lounge/contributor-news

I stand corrected.