Clickworker is one of the better crowdsourcing places to work. They have a human aspect to them and a much better customer service response than say, Amazon Mechanical Turk.
It may take longer to start making money and you may find less jobs available to you than other similar sites. But in time the more jobs you do the more jobs will come. Their jobs seem to be of higher quality and random rejection of jobs are rare, unlike other crowdsourcing places.
You can also get assessments, such as, writing or English language which will open up more jobs for you as well. They are quick to answer any problems you may have and also have a great support system. You are treated like a human not a number.
But like most types of crowdsourcing jobs, it is a place for most people just to make a little extra money. Those who have found ways to make a lot of cash are much fewer. It's best to go in knowing that.