Apparently, this drove one of our readers bananas. He called in and lambasted us about grammar for almost two minutes. Point taken. A nuclear reactor goes on line. (Then it's an online reactor.)
The thing is, we believe we were using the adjectival form when we said, "Online?" (Online buying? Online Sanders?) And, frankly, just as Web site has become website, just as e-mail is quickly becoming email, we expect these computer related terms to keep rapidly changing as time goes on. (Did our caller blow a gasket at America Online back in the day?)
All we can conclude are two things. First, people really do care about grammar, even today. Second, parochial school may play a part in later adult conniptions.