ReMail was more efficient in terms of system resources than Apple's own mail.app, it offered full text searching, and it had other neat features, like autocomplete.
What's going on? Well, it's not a bug it's a feature.
For Google, open source simplifies vendor relationships. You can join the Google software ecosystem without signing a contract. You can exploit Google projects like Android and ReMail and profit from them, because they're under an Apache license.
Just as the Internet takes friction out of the distribution and development process, open source for Google removes friction from the business process.
Why did this not happen before? One reason is you leave a lot of "money on the floor" by doing this. The other reason, of course, is that Google can afford it.
As I have written here many times, Google's advantage lies in its infrastructure. It is the low-cost producer of full Internet infrastructure. This includes more than bandwidth. It includes all the tools and hosting needed to deliver Internet transactions.
This advantage can be exploited against any rival. In this case it is being exploited against Apple.
Until someone is willing to try and match this advantage, and even the phone companies seem for now unwilling to even try, Google will exploit this advantage against all comers.
These advantages lean in favor of anyone with ideas, but they also put a limit on the degree to which you can profit from those ideas. It doesn't matter whether you're a lone programmer in your pajamas or Steve Jobs -- Google's advantages both enable you to bring your ideas to market and squeeze your potential profits like the view of buildings you see on Google Earth.
It's easy for Google not to be evil in such an atmosphere. There is no one for it to be evil to.
But it does make open source start to feel a bit like Orwell's Animal Farm. All pigs are equal, but some are more equal than others.