The right way to do this is by adding rel="nofollow" to the links. Also great advice for any startup displaying user submitted content publicly to the web. Add

The right way to do this is by adding rel="nofollow" to the links. Also great advice for any startup displaying user submitted content publicly to the web. Adding rel="nofollow" to links with low karma will prevent people from spending the time to write a custom spam bot for your site until you have enough traffic to matter for that alone. You'll still get the drive-by spam if it's easy to submit, but you can get around that with an unconventional form.