It's interesting to compare those two examples in the context of the present copyright controversy. In the Visual J++ case, obviously Sun having copyright control over all Java reimplementations would have given them more leverage than just the trademark (though they were able to kill J++ with what they had).

But in the case of proprietary file formats, or really any non-crypto-based attempt to hinder interoperability, the less control, the better. For example, Microsoft could have hypothetically designed their DOC format for the explicit purpose of creating legal issues, such as by having files consist of a series of API calls to reconstruct the document (like WMF!), so that anyone parsing the document would have to reimplement the APIs. To be fair, the need to do so for actual compatibility would weigh heavily in favor of fair use, whereas the story with Android is somewhat weaker (especially because nobody seems to have told the Federal Circuit that Android actually is compatible with existing Java libraries, rather than the API copying being solely for the sake of programmer familiarity...) Also, there is no real need to use copyright for this purpose in the first place: patents have been shown to be quite effective in locking down file formats (c.f. H.264, x86 instructions) - and don't have fair use - so arguably copyright gives offenders nothing they couldn't achieve by other means. But then, patents are limited-duration and who knows, maybe the law with respect to them will be improved some day. No need to hand out extra tools.