>When I pay in cash (digital or otherwise), I know what I give out in terms of value for goods or services. This concept of renting out your computer time on the other hand is vague.

When you watch ads and get data-mined do your really now how much value you pay? I don't think so, it's safe to safe that all of us have no clue about the price we indirectly pay for services we on internet, most of it is just free in appearance.

>How much 'currency' will be mined? Will it be proportional to the goods/services I get to use in exchange? How long will the process take? What if my system fails midway during 'payment'?

The norms are not established yet since it's a totally new way to monetize content on internet however how much you will pay will probably be determined in hashes. Here an example with a new blockchain (Nimiq) of a micropayment you could do: http://coinmiq.com/mine/eyJ3YWxsZXQiOiJOUTI3IFJDNUIgOUU1QSBT...

>This just smacks of convenience for the implementers and as for the user, it exchanges a straightforward system for a murky deal.

I disagree, in my opinion it opens an entire new way to do micropayments on the web.