A seasoned tradeline is a line of credit that the borrower has held open in good standing for a long period of time, typically at least two years.
The Fair Issac Co estimates there are approximately 50 million consumers who re-added as authorized users on other peoples accounts.
For example, Section 817.7005, Florida Statutes states, in relevant part: The risk to the "donor" is that the other person might actually make charges against the account, and not pay it back.
This practice is not yet tested in the courts as the lender now has no way of telling your real credit from that of the former owner who had “seasoned the account”.
While primarily discussing credit repair, the Federal Trade Commission has written facts for consumers to assist them in avoiding scams.