Since it's a negotiable item, as both you and Ron have said, local custom usually prevails. Here in my neck of the woods (southeast Volusia County), the Seller usually purchases the title insurance for the Buyer (the "owner's" policy).
When I'm taking a listing, I usually explain to the Seller that, by providing the owner's title insurance policy, they are showing the Buyer that they have clear title to the property (no liens or judgments against it), and are in a position to sell it.
However, that being said, if I'm working with a Buyer who is purchasing a foreclosure, I suggest to the Buyer that he/she pay for the owner's policy, and the associated search and examination, done by an attorney or title company of their choosing, and insist that the search go back beyond the current ownership.
Otherwise, if the lender selling the foreclosure pays for the owner's policy, that lender will only provide a policy that covers their time of ownership (which could be a few months, or even weeks), and offers little real protection to a Buyer.