Thanks, Scott.
I thought to update the limits to avoid spam.
On my site, it is very often the users reach the limit of posts or votes per hour.
How do I know if a plugin has used cronjob?
I installed plugin Best user per month in one day, but already uninstalled.
Plugins of my site:
Basic AdSense
Q2A embed
Event Logger
Example page
Facebook Like Box
Faq page
Featured Questions
Mouseover Layer
My followers page
On site notifications
OpenSearch Support
Q2AM Next Previous Question
reCAPTCHA
Widget Anywhere
I did not programmed any cronjob.
But I've had other plugins.