At the patterns&practices Summit in Redmond, I was on a webcasted panel, "Open Source in the Enterprise", moderated by Scott Hanselman and included myself, Rocky Lhotka, and Chris Sells as panelists. Part of the discussion came around to building abstraction layers, though, and one thing that deeply worried and disappointed me was the reaction of the other panelists when I tried to warn them of the dangers of over-abstracting APIs.
You see, we got onto this subject because Scott had mentioned that Corillian (his company) had built an abstraction layer on top of the open-source logging package, log4net. This reminded me so strongly of Commons Logging that I made a comment to that effect, warning that the Java community got itself into trouble (and continues to do so to this day, IMHO) by building abstraction layers on top of abstraction layers on top of abstraction layers, all in the name of "we might want or need to change something... someday". It was this very tendency that drove many developers to embrace YAGNI (You Ain't Gonna Need It) from the agile/XP space, and remains a fiercely-debated subject. But what concerned me was the reactions of the other panelists, whose reaction, paraphrased, came off to me as, "We won't make that mistake--we're smarter than those Java guys."
Sorry, folks. That doesn't cut it.
Certainly, .NET has learned from the five years' lead time the Java community has had: the power of a runtime and bytecode, the usefulness of a large and well-built library upon which to build further, the power of compiled-on-demand Web pages, the usefulness of an openly-extensible build tool, even the "one language" vs. "many languages" debate, all could be said to have been influenced strongly by decisions and experience in the Java community. But Java still has much more it can teach the .NET community: mocking, unit-testing, lightweight containers, dependency-injection, and the perils of O/R-M are just part of the list of things that the Java community has close to a half-decade's experience in, compared to .NET's none.
To stand there and suggest that .NET will somehow avoid the mistakes of the Java community just because "we're smarter than them" is more than sheerest folly; it's a blatant ignorance of the well-known and famous quote:
"Those who do not remember the past are condemned to repeat it." --George Santayana