Flickr now gives everyone 1gig of space free the old concept of "Flickr pro" is gone, more space is available but a bit expensive.
Flickr does not permit use of their services for commercial uses, you can not try to sell from your Flickr site or use it to try to advertise another site.
You can make your Flickr images available to the Getty crowd source service,
which will try to sell those images for peanuts as royalty free.
Note that Yahoo the owners of Flickr also just bought Tumbler and are busy messing it up as well
Yes a lot of these services are changing (photoshelter also just made a switch to something they call beam) and the results seem to be more difficult to use on normal desktops. Maybe they are all trying to become tablet/smartphone friendly where you are touch swiping to move around.
A smartphone is all the "camera" you really need.