Photo District News (PDN) have an interesting article where they attempted to identify 5 photographers that they think dominate the 5 most popular photographic platforms; those being blogging, Flickr, YouTube, Facebook and Twitter.
They also tried to ensure that they were photographers only known for their online work.
Very interesting read and don't forget to look at the comments as well... personally I think the list is a little short at five and heavens know why facebook and twitter are considered to be photographic platforms..!......
.....and they should have looked at smugmug as well, for sure we would have got a mention.. ;-)
Anyway, take a look at the article here on the PDN website.