Why I need PVA in For Sale categories?

Everyone knows that craigslist now requires Phone Verified Account (PVA) to post ads under service categories in the USA and Canada. But sometimes craigslist.org asks for PVA even when you try to post under "for sale" or community categories. But why?
Filtering system of craigslist is very complicated and strange. There is no way to know the exact reason for requirement of PVA in non-service sections. Apparently this is IP based. So if you are trying to post on craig's list from an fresh IP address then most probably CL will not ask you for for phone verified account except for service categories for which PVA is always compulsory. But if you are trying to post from an foreign IP then CL will always ask you for phone verification. Craigslist.org has blacklisted some IP addresses of USA and Canada too. If you try to post from those suspected IPs then you may be asked for PVA even for the "for sale" or "real estate" categories.

Is there any way to avoid phone verification for the "for sale" categories?
No, if you are trying to post from blacklisted IP then there is no way to avoid PVA requirements.