At 10 cents per borrow (no idea if that number is right or not but it seems reasonable enough)...only the authors that don't value their time very much.
The average book will have at most 2-3 copies but even if we assume 10 for arguments sake you'd earn yourself 1$ per library that you visit.
Given that you have to get to the library, spend time checking the books out and returning them and only get a cut of X% of that one dollar to boot it seems like a pretty futile exercise :D
The tricky thing with digital lending is that anything online that is capable of abuse via scale will be subjected to it. If the fee for one borrow is $X and the cost of buying one borrow on Mechanical Turk is $Y, if $X > $Y then someone will arbitrage.
I think the point is that if such a system were adapted online, it would be prone to abuse. It's easier to "check out" content digitally then it is through a traditional library.
The solution they've adopted in Sweden is that each library card is only allowed to make n digital checkouts a month for some low value of n.
Although the problem they where trying to solve wasn't so much abuse as the fact that the service was far more popular than they'd anticipated and legitimate use was high enough to seriously risk their budget.
The average book will have at most 2-3 copies but even if we assume 10 for arguments sake you'd earn yourself 1$ per library that you visit.
Given that you have to get to the library, spend time checking the books out and returning them and only get a cut of X% of that one dollar to boot it seems like a pretty futile exercise :D