A point came up at the UK SharePoint User Group Chrismas drink, about Personal sites and whether they were top level sites i.e they exist as records in the Sites table and are the top level container for all its subwebs, I hadn’t checked this in v3 so a quick check with PowerShell and stsadm confirms that this is still the case as in V2

Assuming http://sps:20488 is where your personal sites are hosted calling stsadm -o enumsites and processing the returned XML in PowerShell gives us

PoSH C:\demo> $output=stsadm -o enumsites -url "http://sps:20488"
PoSH C:\demo> $xml=[XML]$output
PoSH C:\demo> $xml.sites.site

Url : http://sps:20488
Owner : CONTOSO\administrator
ContentDatabase : WSS_Content_11fba01f-f0c4-4a05-a3c3-868499fd31ce
StorageUsedMB : 0.6
StorageWarningMB : 0
StorageMaxMB : 0

Url : http://sps:20488/personal/administrator
Owner : CONTOSO\administrator
ContentDatabase : WSS_Content_11fba01f-f0c4-4a05-a3c3-868499fd31ce
StorageUsedMB : 0.7
StorageWarningMB : 80
StorageMaxMB : 100
Etc…