I tried to come up with good number of how many times those ads get shown, but it is somewhat complicated - so I will assume that Facebook and Google always show, and Wikipedia does show only 10% of the year. I will not involve ethics or relevance argument, as I don't support 100% of WMF direction either :-)
Hmm. Could we use better link in Sidebar (with WMF logo or another image)? Better than simple "Donate"
przykuta