While you bring up buying more SP to increase limits. Do people leasing SP from others in form of delegations get increased bandwidth while they are leasing? Clearly some users will never use all the bandwidth they have even more so if they are not very active.

I think a bigger limits on new users could increase the amount of spam and more importantly encourage spammers to try and bypass protocols put in place to limit it to 1 free account per person if they are unregulated in terms of bandwidth.