If there is, it is not a problem to the forum.
If it was to be a problem, theymos would have edited the forum code such that you cannot post if you do not have upto 5mins delay after a previous post.
Since there's nothing like this implemented, it therefore means that post bursting isn't a problem.
Burst posting is a problem in itself as it will never help you make a constructive post.
For example, can you make let's suppose 4 good posts in a matter of 30 mins in different threads? You need to read the few posts above, understand the conversation and then post your point of view. If you are not doing this, then you're only posting to complete the quota of the campaign in order to get the payment.
By the way, you cannot survive long in a campaign with the habit of burst posting as good campaign managers will soon identify your behavior and replace you with those who pay attention to the details.