"The determination of any taxable benefit in these circumstances should take into account the respective rights and interests of both the corporate policyholder and the designated beneficiaries. Where the designation is revocable, the policyholder continues to retain all contractual rights and benefits under the policy, including the right to name and change beneficiaries, transfer or surrender the policy, collaterally assign the policy, and obtain policy loans. The designated beneficiary only has a contingent interest in the death benefit, which will only be paid if the policy remains in effect, the beneficiary designation is not subsequently changed, and the beneficiary does not predecease the life insured."