Good discussion all. Lots of great insights and perspectives being shared.
First, there is the the theoretical discussion of what "should" be vs. what is actually practical and what can happen.
Getty, for all my criticisms about them, are still somewhat smart about this. They have created this little money-making machine and have made a ton of money without the PR exposure Righthaven attracted.
I hypothesize that there are multiple reasons why Getty hasn't fired off lawsuits yet.
First, the obvious escalation would bring in folks like EFF and more defense attorneys into the fray. If they think Oscar has been a thorn in their side, can you imagine more defense attorneys jumping in like what happened with Righthaven?
Second, no matter what the companies may have you believe, there is no sure thing in court. You never know what the other side will bring. Being a larger company, in many ways, they have more to lose than one case. Righthaven has shown that the occasional loss and bad karma can be very devastating. One loss for Getty Images for whatever reason would be very damaging to them.
Third, the actual cost and recovery would be low going after most of the letter recipients. It is difficult to believe that a judge would give Getty Images any more than $10,000 including legal fees for most single-image infringers. And assuming they got the judgment, how easily would it be to collect?
Fourth, sending threats and actually pulling the trigger would actually help expose the names of the employees and individuals involved. Corporate employees are notoriously cowardly and only care about their jobs and their salary. I know this and this is why I look very hard for WHO makes and executes the decisions of a company. They can say Getty Images all day long but ultimately it is the individuals who is responsible.
For example, Steve Gibson thought he was so smart. But he is probably one of the most hated men in the biz today. That hatred will and continue to manifest itself in strange ways. Already, the anonymous strangers have created a mindshare on the Internet to join forces against him, Stephens Media, and what he represents. Yes, there is some paid effort being expended but there are a ton of energy and time being expended to "get them". Be very careful of those people who decide to take up a cause for its own sake and not for the money.
I could go on with other esoteric reasons but I am convinced that these intangibles would manifest itself in a real way.
Having said all that, the diversity of letter recipients and their individual responses/reactions are very different. As SG pointed out, there is not yet anything tangible to defend, simply the possibility of a lawsuit. But to defend against that possibility comes having a spine, some diligence, and a lot of learning.
Ultimately, you cannot always "convince" someone to see your way. Sometimes you simply part ways to agree to disagree. And I believe that happens very often from people who don't bow to the letters.
Anyhow, I am rambling but I feel better now.

Matthew