Agree sammie.
The present greet system is an old one. Huge changes need to be made to it. At the moment, it might still somehow work in dating sites, but is completely useless for social networking sites.
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How about replacing it with 'Teasers' of orkut? In orkut, a 'send teaser' option is shown on every profile. When one clicks on it, the teaser page opens up. There either the user can write his own teaser message, or may select one from the provided categories like- sincere, romantic, humorous, see more flirtations, movie lines.
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This would be a good feature, and moreover the admin can be provided the power to manage the teaser categories and add,edit, or delete teaser messages from them.
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One more important part can be making all this load in an ajax window like the new login box in dolphin, instead of a pop-up window. When a user clicks the option 'send teaser', an ajax window opens in which the user does all similar to orkut. Once the teaser is sent, the ajax window disappears. This will also speed up the task, and members wud love 2 send teasers. Moreover, there wud be no more a file like greet.php and so no worry from bots.

Please do comment.