I thought it might work because anonymous users are automatically
authenticated as IUSR_computername. I know it doesn't work on regular
sites, but thought it might on MySites. Anyway, you can turn on
Anonymous access in Central Administration on the Operations panel in
Authentication Providers. Then go into site Settings for a MySite and
turn on Anonymous access from the Settings menu of Advanced Security.
The problem is that since each MySite is a Site Collection you will have
to set it on each individual MySite. Some of these settings can be
defaulted prior to creating the MySite by navigating manually to the
_Layouts/Settings.aspx page of the root of the MySite provider and
setting things there. But I tried that and it doesn't look like
Anonymous Access is propogated to the other MySites when they are
provisioned like some of the settings.
You could probably write a WEB scoped Feature to modify the
AnonymousState property of the SPWeb, then staple the Feature to the
MySite template and set it to autoactivate. Then when the site is
provisioned the Anonymous Access capability would be enabled.