When I was single I would have had time for 3 of them - total in my life. I think systems should automatically block all requests for notifications if you already have 3 since it is not possible for more than that to be useful. (the exact number is debatable, but 3 is close). Note that I said systems - I want firefox, chrome, ie, safari to work together across all the computers I have to keep the number down - for security reasons I understand they cannot but that would be ideal.