NB: It is better in any case to limit to a reasonable number all the actions add by indicating this time a counter. For example, 25 per hour. So that while you sleep, a spammer can not flood the site, it is better to prevent than cure.
Up: depends on actions, for videos better put 10 for 24 hours for example.
Re-up: It is also a good way to limit spam by email, in dolphin there was a security of 60 seconds between two messages, here nothing, so pay attention to that, impose a maximum limit per hour.