Malinvestment is a problem at any large organization. I don't see any reason to believe this is nefarious or unethical. Nor do I grudge Wikipedia for being to incredibly efficient at running their core business that they so easily outraise their needs. Raising money to grant to other organizations is a very common model in the charity world so it's hardly unprecedented either.
I think a distinction should be made between a foundation and a charity. A foundation uses an endowment to fulfill the agenda defined by its charter on the society. Only a small portion of the foundation's capital is used each year, as the foundation aims to be a more or less a perpetual organization.
A charity generally uses all of its annual income on its "cause", and needs to constantly raise more capital. Wikimedia sure seems to behave more like a charity than a foundation despite its name. I find this regrettable because it is probably the only non-profit internet organizations whose fundraising volume would allow it to behave more like a true foundation if it chose so.
