The minimum payout seems to be a cent.
You could make more money gambling with btc...and with less effort. Not that I would recommend doing this, either...
They aren't bad if you do them passively. Each site takes 5-10s so you spend about a minute every hour or two. The good thing is that as BTC goes up in value, so will your earnings. So what is worth 13 cents today could very well be worth dollars later on.
But you can earn dollars now at minimum wage, put $1.00 into BCN and have money now later on have 7 times the 13 cents.
Those tini wini payouts are taking advantage of you.
Sorry, I figured the time I spend at work counts as earning money. Spending a minute every couple hours on the sites doesn't bother me at all. I usually do it while I'm watching tv. It's downtime regardless, so anything is better than nothing.