Sorry, forcing a download of an entire album is *not* giving you an option that "you don't have to tune into". This is not you giving the kids an album you like, this is you strapping them to a chair to listen to it à la "Clockwork Orange". If everyone got an email saying "Click for a free download of the album!" there would be no complaints. (Mockery, perhaps, but not complaints. :-) )
Except this is pretty much exactly how the system was setup.
In "releasing" the album, Apple pretty much just added a database entry for every user on iTunes to say that they had already purchased the album. It was then supposed to show up in your iTunes library as "in the cloud", with an option to download it.
Nobody was forced to download the album. The only way you'd download it without needing to do so specifically is if you had previously turned on the option to automatically download all new iTunes purchases (which defaults to off). And the only way you'd have to worry about using cellular data for this is if you had the option to download iTunes Music purchases over mobile enabled as well (otherwise, it would wait until you're on WiFi). So yeah -- this is completely a tempest in a teapot from people who don't like U2 seeing a free album available for download showing up in their libraries.
Hopefully Apple have learned their lesson. It was a publicity stunt, and while it upset some people, here we are talking about it. I don't think it went off the way they were hoping it would, and hopefully they've learned some lessons in the process.
 - Here in Canada at least, it appears the setup for this album didn't work for a very large number of users. I know in my case, the U2 album did not show up on my iPad as it was supposed to, nor did it show up in any of my iTunes libraries. And I do have the auto-download option enabled. In order to get the album, I had to go into iTunes and find the section that shows all your existing purchases, and then select the "Not on This Device" list, and only then could I download the album. And looking at the album reviews on iTunes Canada, it seems that I was hardly the only person to experience this -- nearly every review when I last checked last night was form people trying to figure out how to get their "free" album. I haven't seen this level of complaints outside of Canada, so I'm assuming either a) something screwed up with the iTunes Canada edition of the album's launch, or b) iTunes Canada did something different in order to not run afoul of some legislation (although I can't for the life of me guess what legislation that might be). This situation seems to have been lost in the noise of everyone else complaining about getting a free album, so I haven't heard much commentary on the situation.