In essence it's no different to any other type of customer loyalty scheme, and in that sense the advantage (as I see it) is that it tips the balance marginally in favour of voice as opposed to exit. So investors may actually have a grumble to management rather than simply flogging their shares to another investor, and thus may encourage the board to address issues of concern.
Investors can of course still flog their shares if they want to, but by marginally tilting the balance in favour of holding this would hopefully address the problem of asset managers generally choosing the exit option when they don't like management, leaving the problem unaddressed. Also it would be up to each company decide whether such a scheme was valuable, rather than the approach of a Tobin Tax - to make exit less attractive, rather than voice more attractive - which would hit everyone. So there could be a bit of experimentation and if it doesn't work it's easy enough to scrap.
I'm sure there are some obvious problems - so what are they?