From a pure economical perspective, simply no.
specialized APU's or GPU rigs will always be magnitudes more efficient than some JS script running in a browser instance.
so you end up letting 10.000 people pay the same amount in electricity that 1 person could achieve with his specialized rig. The price of electricity and hardware is the limiting factor in coin generation.
So , is my rig chums along for a year and produces a whole dollar worth of coins, others will have spend 10.000 dollar on electricity, to produce that one dollar.
For now it seems like "free money" for the site operator, it is not his electricity bill, but others are, and will soon realize the idiocy in this scheme.