I think it's a weak argument, actually I think it's a slippery slope if CEOs can't say anything without that implicitly granting all sorts of permissions. It's a valid defense that Schwartz obviously meant to welcome Android to being based on Java, assuming they didn't infringe on Suns intellectual property.
"I'm happy people is so excited about watching our movies" is not an endorsement of pirating said movie.
I am not a lawyer, but I completely disagree when estoppel is taken into consideration[1]. Sun publicly endorsed Google's implementation of Java and there is probably plenty of evidence it endorsed it privately as well.
There is a reason a CEO doesn't just spout off whatever he wants without consulting a lawyer. Especially on company letterhead which is what the Sun Blog amounts to these days. If it was a mistake it should have been retracted. But it wasn't, so maybe it wasn't a mistake in the eyes of the law.
And yes, if a film's rights holder gives explicit or even implicit endorsement of people watching the film through piracy, as did Michael Moore [2], that does protect you from him suing you for pirating it. You don't need a license contract to tell you it's OK.
Estoppel is meant as a protection against the following situation. Sun tells Google, "Don't worry. Android doesn't infringe on our intellectual property." Google then relies on that information when making future plans for its operating system. Sun then comes back and says, "we're suing you for infringing on our intellectual property." Sun (now Oracle) would be reasonably estopped from collecting damages because they had earlier made assertions that Google reasonably relied upon in their decisions.*
Google's lawyers note that Sun offered to license Java to Google (http://www.networkworld.com/news/2011/072211-google-sun-offe...). Therefore, there is no reasonable way that Google could try to claim estoppel. Google was aware that Sun believed that Google needed a license. Therefore, there is no possibility that Google believed that Sun was saying that Google's Java implementation didn't infringe on Sun's IP.
There's a distinct difference between that scenario and the one that occurred. In the hypothetical, Sun has stated a fact "your implementation of Java doesn't infringe". Later, Sun changes that fact "your implementation of Java does infringe". With what Sun's CEO has said, one can create a dialogue that doesn't contradict itself. "We're happy you're using Java"; "We're still happy you're using Java, but you have to pay for its usage or code around our patents like we said before when we offered you a license for Java."
*Estoppel is meant to make sure that people can't trick you into situations (and often times requires some proof that the person being estopped had that motive). For example, let's say that Sun had gotten together in a board room and started saying, "we'll tell people that there are no patents on Java and they can all use it for no charge and then later, once they've all started using it due to our assurance that there are no patents on it, we'll change our mind and sue them for patent infringement." That isn't the case here.
I originally clicked reply to a similar message to say much the same thing as what you've said, however the original announcement that he was replying to gave no specifics, save one-
"Thanks to the availability of our Jbed™ Java™ VM on the Android platform, we offer immediate compatibility to the standard Java ME world to enable Java ME-based mobile services with the Android platform."
So it's a bit fuzzy. I'm on the fence as to what this means, but given that Android was actually based on Java prior to Google's purchase, and this was not long after that transaction, I have to think Schwartz really was referring to a J2ME implementation. Indeed he specifically talks about support for netbeans and the like, which of course is entirely untrue for today's Android development.
So I don't think this is the smoking gun that many think it is. Scwartz perhaps jumped the gun before formalling licensing it, but it isn't some grand endorsement of an Apachy Harmony derivative.
The crucial difference between this situation and the one that Google is in is that the activity the Sun CEO refered to was the allegedly infringing activity. "I'm happy people are watching our movies" wouldn't be a cause for invoking estoppel, but "I'm happy people are bittorrenting our movies" would be.
Also, in this case the crucial aspect is what the law is, not the quickly considered opinions of non-lawyers like us.
"I'm happy people is so excited about watching our movies" is not an endorsement of pirating said movie.