[Wilya]

There's a noscript fallback. If w3counter does it's job right, people without javascript should be counted.

Those who explicitely block w3counter wouldn't, but that's few people, unless it's in an adblock/ghostery/... blacklist.

[phaylon]

I'm using RequestPolicy, which I'd assume also hinders tracking even without being somehow explictely blocked. No idea how wide-spread those extensions are though.