If browser mining was a good deal for the end user the vast majority of its proponents wouldn't feel the need for stealth.
Paul Graham might disagree;
"The two most important things to understand about startup investing, as a business, are (1) that effectively all the returns are concentrated in a few big winners, and (2) that the best ideas look initially like bad ideas." (emphasis mine) [From http://www.paulgraham.com/swan.html]
Stealth is not necessarily a sign something is bad; it might just be hard to persuade people that it's good, and that's a reason to be stealthy.
I'm afraid the doctrine of "if it looks bad, it must be good!" is not in fact true or generally applicable. And it's not what Graham is saying, for that matter. If you read a bit further:
"It also reminds you that the vast majority of ideas that seem bad are bad."
The idea of running up every web browsing computer to 100% CPU, costing them tens of dollars in electricity while giving you a few cents of cryptocurrency, seems bad and is bad.
Paul Graham might disagree;
"The two most important things to understand about startup investing, as a business, are (1) that effectively all the returns are concentrated in a few big winners, and (2) that the best ideas look initially like bad ideas." (emphasis mine) [From http://www.paulgraham.com/swan.html]
Stealth is not necessarily a sign something is bad; it might just be hard to persuade people that it's good, and that's a reason to be stealthy.