At 25 cents a look up, the spammers will mostly go away and legitimate interests will be more than willing to pay. (unfortunately, some of the worst criminals such as stalkers will also be willing to pay as well).
This would only result in someone paying for it (once) to create a database and then selling that for smaller sums to all the spammers/scammers. And as you mentioned, stalkers are just as bad or even worse.
However, free whois services are very still very useful for the purpose they were intended to be used and hence shouldn't disappear completely. Just let people have the choice between private/hidden (rather small/personal websites) and public information (rather companies).