Depends completely on the property (location, condition, design, etc. etc. etc.). Most pre-foreclosures would be short sales if the owner put it on the market, so you have to assume in a pre-foreclosure sale that a lender may get involved.
I do several unsolicited offers on pre-foreclosure and standard properties each year and I've yet to get a response when starting at about 65% of FMV. Unless you can verify the owner has a lot of equity and few choices, 65% usually won't be taken seriously.
But if the situation is right, why not?