People value things more when they feel a sense of ownership.
Also know as the endowment effect or divestiture aversion.
Can you give people something that is theirs only on your website? A page with their own content or personal data? A public page for them to show what they are doing at your website? Create something that is theirs alone and they'll value it more then it's actually worth.
On the other hand: keep in mind that if you want people to switch from another system/ product/ competitor, keep in mind that they'll value their current (and thus 'safe') choice more then they actually should, so be extra convincing in telling them you have the better product/ service.