Edit: I made a mistake in my calculations and fixed it.
I have been a member of the wordpress support forum for 8 years and using wordpress since 0.71 and b2/cafe press before that.
I have tested this plugin since 01 Jan 2012. Total payouts generated: 486
I have sent email to Donny the developer without response.
I must label this plugin as a scam with the following evidence. No one item is unfair, but the lack of upfront disclosure and the poor payout practices make this plugin a scam.
Between Feb 4 and 6 the payout amount from this plugin was reduced 5.201600492% without explanation or alert. Reductions in payout % are designed to allow the developer to adjust for changes in difficulty, but 15.938864629% payout reduction since January is not reasonable. This is beyond the difficulty changes in bitcoin mining over the same time.
There is a 0.01BTC charge to withdraw any bitcoins from bitcoinplus. Donny claims this is the amount charged by the network and he keeps none of those coins. The current charge is 0.005BT so this charge is 100% markup.
You can only withdraw a multiple of 0.01BTC. You may never withdraw the 3-8 decimal places from the site.
So in order to generate a payout of 0.01BTC you must generate more than 0.02BTC to allow for the charge. If you have enough traffic to generate a payout of 0.02BTC you'll need to earn 0.03BTC. So the longer you wait to withdraw the less the fee is as a percentage of the payout.
Today the BTC price is $5USD in order to get a USD$0.05 payout you must earn $0.10 in increments of $0.000154 so 649 payouts per $0.10. Not every visitor generates a payout. It is actually quite hard to generate a payout. As the payout must be in incements of 0.01BTC you may have 648 payouts and be unable to withdraw them.
The drop in payouts is illustrated as
Coin generation (via external website) Me 0.0000308 BTC Feb 06, 2012 10:35 PM EST Complete View Coin generation (via external website) Me 0.00003249 BTC Feb 04, 2012 6:32 AM EST Complete View