[chii]

> Right now it's incredibly hard for sites to reliably know if someone is using adblock.

no that's not true - it's "easy", as long as you have cooperation from the advertising network. Their ads could do some callback onto the main page.

[swhipple]

You can do it yourself as well -- EasyList and some others have patterns that they check for on the page path and individual elements, not only known hosts.

[manigandham]

Keyword "reliably". It sounds easy but it's not due to the all the different plugins, rules and levels of adblocking.

There are also constant updates to counter this. If you check the adblock forums, there are dozens of threads every day about how to get around checks on sites and even disable messages that specifically show up to adblock users.