Generally, to be able to write off worthless securities, you need to show that they're indeed worthless. It's not necessarily easy, as you need to prove that there's no way they will regain any value in the future.
in 2008, the Treasury adopted regulations saying you can establish the worthlessness of securities by abandoning them. The regulations do not explain the steps that would constitute abandonment, but it seems reasonably clear that gifting or donating securities is not the same as abandonment: you have to give up all rights to the shares, including the right to determine who would enjoy the benefit if they somehow recovered value.
http://www.fairmark.com/capgain/worthless-2.htm