This sort of anonymous donating has happened since 2010. Theymos even mentioned it as a problem back then. The developers have done various things over the years to try to fix these, but they never truly seem to go away.

The difference today is that these are now more than just annoying and, rather, malicious in nature since they are capable of publicly identifying owners of coin.

I keep getting random influxes of BTC....five cents here, 1BTC there....I can only assume they're from people on the forums, as I know no one who uses bitcoins.  Thanks to whomever it may be.  I'd really like to know who.