When a business becomes serious? Do you need to hire several workers to look legitimate? If that's still not enough, do you need to make yourself a slave of VC?
Only problem I can see is that one man operation is susceptible to the run over by a bus scenario.
However that is still better than a woke VC asking the "owner" to cancel some users.
I would seriously prefer a service like this to be run by a two man team. Or at least have a guarantee that I'll get automatically notified if something happens to a sole operator.