Hi Michael,
Just to add my 2 cents to Cheli's reply. Yes, you absolutely should limit the number of emails you send to your customers (or prospects and leads, for that matter). Why? To prevent customer email fatigue, to send only the most relevant message, and to prevent damaging your deliverability score.
How to implement it? Each company will probably do it differently but I would suggest you think about using segments (or target audiences) vs. a global filter in Eloqua. The more granular and specific your audience, the easier it will be for you to implement a strategy to 'suppress' contacts from receiving multiple messages within a certain time frame.
What do you mean by, "how do you say no when people ask for exceptions?"
-Azucena
P.S.
I actually submitted a proposal to present on our master suppression strategy at the Eloqua conference (crossing my fingers to get picked!). If so, I'll let you know in case you're there