Generally, anything that directly or indirectly involves a right of property is assignable, with the exception that rights and liabilities under an executory contract for personal services, or contracts involving personal credit, trust or confidence, cannot be assigned.  If the rights arising out of a contract are coupled with liabilities, or if they involve a relation of personal confidence such that the party whose agreement conferred those rights must have intended them to be exercised only by him/her in whom he/she actually confided cannot be transferred.  When the assignee of an executory contract can perform the duty imposed by the assignment as effectively as could the assignor, the fact that this duty is personal cannot be raised by the defendant in a suit by the assignee on the contract.[i]

[i] New York Bank-Note Co. v. Hamilton Bank-Note Engraving & Printing Co., 28 A.D. 411 (N.Y. App. Div. 1898)