For me there's a little bit hard in mining because we dont know whether the sites are paying, but I saw also more people earning in many sites. I hope there's a sure mining already and no scam site.
Some people use mining sites to mine for fun or to get more bitcoin. If you want to mine bitcoin you need more time to wait to gain that much bitcoin but you can a sure that you gain that. I hope that all mining sites will continue their giving free bitcoins.