I think businesses are walking a fine line when they start implementing measures such as this. Sure, the businesses do have the right restrict access to pop-up blockers, but customers also have the right to say "we're not gonna put up with this."

In my opinion, the businesses that have a problem with pop-up blockers need to take a serious look at their business plan. If a company is SO DEPENDANT on pop-up revenue to pay their bills, they are just asking for trouble. If a fast food restaurant said that "You have to read all the ads we painted on the windows before we'll let you see the menu", you'd laugh in their faces.

Legitimate businesses that have solid business plans do not have any problems with this. The people complaining are those "free sites" (informational, charitable, tutorial, etc.). Maybe it's the capitalist in me, maybe it's the Darwinist... but I say this is a prime example of "Survival of the Fittest". If the cause/knowledge that the free site is supporting/promoting can't solicit enough support from the viewers, the site goes away. If there is enough of a following to provide the support/resources needed to keep the site afloat, hooray!... the cause/site has proven to be worthy.

Bottom line is that I think these are just consumers standing up for their rights.