I tried to use Shutterstock, and think it’s too picky and difficult to use. *submit exactly 10 images, not one more or less, *images must be at least 4 mpixels (I have some beautiful ones they said no to, for being too small), *must include at least seven keywords describing each. Come on, it’s a simple picture, not an entire magazine article!
At first I found that hard to believe.
Then I read http://submit.shutterstock.com/guidelines.mhtml and found this to be true.
I guess since they’re in the business of selling digital images they want to filter out anyone that’s more a hobbyist and not a professional.
Maybe someplace like snapfish or photobucket is more what you’re looking for?
They have big prices and lots of photographers would like to post photos there so, like Mittineague said, they avoid those that post a picture and leave.
Almost the same happens with istockphoto.com
That’s true, but on the other hand, it’s a relatively good deal if your photos are clicked by users quite a bit. If you end up making $500 or $600 off of a quick photo and taking the 10 minutes to re-size it & come up with 7 keywords for it, you get ahead quickly. As for the 10 photo minimum…I guess I’d rather do them a little at a time- as I find the time, but then again, I’m sure they want to ensure quality & getting those 10 could help them see a broader spectrum of your work. Now that you’ve brought up this subject…I might do a bit of a comparison between companies & submit some of my own! I hope you’re able to find a company that works for you. If you find another that seems to have better regs, let us know! 
Shutterstock developed this system before the microstock stock photography model evolved. Back in the day (2000- 2006) a stock image could licence for $50 to $100. Today this image sells for $5. My point is when they developed this system the investment in time to upload, tag and keyword was worth it, today the ROI on time spent uploading to these sites may or may not be worth it. Best way to upload larger volumes is to automate your uploads, like using excel to hold your metadata.