Certainly looks like it..

Maybe it's driving type?

I've noted this too. Somewhere around 4k it looses the 'like new' look and gets progressively darker when 10k+ it starts to look 'dark' and when drained seems slightly thicker - likely just a visual trick due to color. On Syn oil. When tested through I've not had an oil come back that was under performing.

Honda seems to think their filter will go 15K. If you note they recommend changing the filter every 2nd oil change. Which if done at 7500 miles would be every 15K. Mobil 1 EP oil suggests you use their filter and go no more then 15K. The S has almost 5QT and a rather small filter.

Could filter technology be the weak link?

 

A filter cannot filter out soot (usually what causes the darkening of the oil), its just to small (and suspended within the oil). The filter is trying to catch "large" particles that would clog or damage parts if circulated through.

If you think a S2k filter is small look at some of the Nissan's....

 

The filters use to be a huge weak link before synthetic fibered filters came about.

 

i keep it simple. i do my oil changes every 3k. synthetic or not.

sometimes your engine burns oil, drips oil. whatever it is. if you're low on oil, and you replace it at 3k. you're safe. (in most cases.)