Duplicate contact records created by Online Contribution and Event Registration

When an anonymous user submits a contribution, membership signup or event registration - we create a new contact record even if there is already a "matching" contact record IF the Contact Matching rule is set for "Email" only.

To recreate:
1. Modify Contact Matching rule to be "Email" only (this is a fairly common configuration since it works nicely for folks mostly doing newlsetter list signups etc.)
2. Create a contact record:

• First name = Dave
• Last name = Greenberg
• Email = dave@civicrm.org
  3. Log off or go to another browser and submit an Online Contribution using the above info (test-drive is fine)
  4. There will be 2 records for Dave Greenberg - the contribution will be associated w/ the new (2nd) record

The same behavior occurs during Event Registration.

NOTE: When I discussed this with Lobo - he had thought that we were ALWAYS matching on Email Address during this processing. If this is the "desired" behavior (and I think it makes sense given that we can't be sure we're collecting anything other than Email Address) - then a second case is also "broken". If you submit a contribution using an email address that belongs to an existing contact which does NOT have a First or Last Name value - we also create a duplicate - even if Contact Matching is set to the default of "First Name + Last Name + Email".