This is exactly what I do and I've switch friends and family over as well.
Whenever they bring up the perceived inconvenience (which goes down on the desktop with practice) I simply remind them how much time they will waste if one of their accounts is compromised.
Sure their foursquare (or pick another random service that doesn't hold EXTREMELY important data) account isn't that important but when it uses their Gmail address and has the same password they are just begging for trouble.
Also this gets them out of logging on to their Gmail and Facebook accounts from public computers. They still don't fully understand the possible problems but at least now it is such an inconvenience they just use their own devices.
Whenever they bring up the perceived inconvenience (which goes down on the desktop with practice) I simply remind them how much time they will waste if one of their accounts is compromised.
Sure their foursquare (or pick another random service that doesn't hold EXTREMELY important data) account isn't that important but when it uses their Gmail address and has the same password they are just begging for trouble.
Also this gets them out of logging on to their Gmail and Facebook accounts from public computers. They still don't fully understand the possible problems but at least now it is such an inconvenience they just use their own devices.