If it takes 5 hours to produce 0.0003 BTC
Then 33 x 5 or 165 hours to produce 1 bitcent
Which is worth less than a dime
Average computer uses 200 watts
That's 1 kWh every 5 hours (200W = 0.2kW; 0.2kW * 5h = 1kWh)
Or 33 kWh to produce a dime
Most people pay more than a dime per kWh
So this is a way to make someone else pay $3+ to earn you a dime
Why not just have them mail you their empty soda cans ... They will pay $3 in postage and then you can go recycle them for a dime
The economics are the same
That's based on the assumption that people are running this on a computer that would otherwise be off. It's pretty good about CPU priority, my computer is perfectly usable while this is generating.
What's the math behind an idle computer and a CPU maxed computer?
And yes, compared to GPU mining CPU mining is inefficient - but this is something that could get people interested in bitcoin who otherwise wouldn't take the time to set up a miner. I'm thinking of this as a kind of entry-level miner (at least until there are ways of doing GPU mining from the browser).