Jobs on micro workers

No doubt that it is very nice to do the tasks on micro workers. but why number of jobs related with sign up, face book, twitter, yahoo answer, and some other simple types of task are very less? I have noticed that the number of jobs related with forum post are more in comparison with other. Is it the availability problem or some other that i do not know. I shared as I experienced. Thanks

it is because the jobs like sign up,facebook,twitter are really easy to do so many of try to complete these jobs as they can.the hard one is left behind for long time.

Good sharing.
It's a good thing to share our experiences and feelings to other as well as friends.