Simple version is no.  Using the free tier you won't earn even a penny a week (USD).  Technically you are right it is free but it really isn't worth it.  If your lucky you will get maybe a penny each month.  I would recommend spending 30 minutes in a parking lot looking for change on the ground it likely has a higher return on your time.  When ASICs hit you will be lucky to make a penny per year.

Using anything other than the free tier you will simply turn a large amount of USD into a smaller amount of BTC.