Deborah H. Schenk (NYU) has published A Positive Account of the Realization Rule, 57 Tax L. Rev. 355 (2004). Here is the Conclusion:

In summary, although a realization rule is an inevitable feature of our hybrid tax, a pure realization rule is indefensible in a system intended to impose a tax on capital. Differing effective tax rates on the return to capital give rise to deadweight loss and a misallocation of resources triggered by efforts to limit avoidance options created by the rule. Since the benefits of the realization rule are not fully capitalized into prices, different types of income bear different effective tax rates, creating equity concerns as well. Since neither an accrual tax or a pure realization rule is tolerable, the task for policymakers is to determine where along the continuum to draw the line.