Some Eloqua clients do this to get around duplicates between SFDC Leads and SFDC Contacts, reduce Salesperson workflow process (converting "Leads" to "Contacts with Accounts") and to rely less on deduplication vendors.
In one scenario, I've built a front-end form process where the new organic contact that submits a web form is able to self-identify their SFDC Account ID by use of custom PHP and Salesforce.com API that allows the user to choose an Organization by the zip code provided earlier in the web form. That selection populates the SFDC Account ID in a hidden form field and the SFDC Contact is created with it's preferred SFDC Account via Eloqua's external call mapping on the Create Contact call. This is an ideal situation, but doesn't work for all businesses.
What have you done in this situation? Allow Eloqua to create an SFDC Contact as an orphan without a SFDC Account linked? Use a default SFDC Account ID that all contacts integrate to until a salesperson matches them to the correct SFDC Account? Has anyone created a automated matching algorithm besides the zip code one I mentioned above or have you been relying on a Vendor for matching?
How are you matching a form submission from a Fortune 1000 company to the existing Account in Salesforce.com?