If I bought a PowerPC with the understanding that it would be supported by OS X, then I would expect that it would be continued to be supported by OS X until the end of the product. That would, in my mind, include Snow Leopard (i.e., OS X SP6).
The focus of Snow Leopard is adding better support for multi-core processing, 64 bit processing, and GPU co-processing. It seems like it draws a clear line in the sand -- the kind of radical change that belongs in a major rev.
Ultimately, maybe it's a trivial thing. Who cares if it says OS X or OS XI on the box, right? But to me, it's misleading to consumers. There will be "Snow Leopard or higher" dependencies as software is written to take advantage of the processing capabilities. For PowerPC users, there would be no upgrade path -- certainly that's not part of the original value proposition. This IS bad form, because the rules do not apply to technological innovation, but rather to customer service.
I have no political agenda here. I own two Macs, three iPods and will be buying the iPhone 3G.