The computers are already on a 10/100 switched network along with 2 other Macs. I was looking for the convenience of not having to power up one computer to use the drives. If they were shared, either computer could see them if the other wasn't powered up or both could see them if both computers were on.
Also, when the newer FW drives with ATA100 bridge chips in them start shipping, I'd be looking for the faster speed that my network couldn't give me. I don't want to bring in digital video over ethernet.
As I said in the original post, I could physically disconnect the drives and move them to the other machine. Both G3s are next to each other and share the same monitor and keyboard already. I just figured it would save some wear and tear on the drives to not disconnect them all day long.