Just as you can have a field on the Account Card for the Source of how this Prospect / Lead / Suspect was entered into Synergy, you also have the ability to enter a Source for each and every Sales Opportunity that is created / tracked.
Using this field can help Marketing determine where new sales opportunities came from, such as an ad campaign, conference booth, mailings, web site inquiries, etc.
On any single opportunity, you may have only one source identified. Searching on this information can be easily done by your marketing department by using the Opportunities: Pivot Analysis and selecting as the rows and columns, the values Opportunity: Source and Account: Account. Of course, you may filter dates, sales cycles stages and other fields.
A Marketing Person can not only review the number of Opportunities, but also the dollar value.