If sites started doing this (using a visitor's GPUs and Litecoin more likely), the downside to a consumer is the extra cost in electricity (which goes to electr

If sites started doing this (using a visitor's GPUs and Litecoin more likely), the downside to a consumer is the extra cost in electricity (which goes to electricity co, not the website) and lower lifetime of hardware. If it's all opt-in, it's up to the consumer whether they think it's worth their cost to "support" the website. I don't see an offer of removing ads as a benefit because that can easily be done by just installing AdBlockPlus, the real benefit is feeling good about "supporting" a site. (And unless they happen to have a good GPU they'd probably support the site more by just clicking a few ads, or actually sending them real money via any of the micropayment services including bitcoin.)