You began by making comparison to newspaper circulation, and have just said "but I am not convinced that the web is anyway near as effective in selling to viewers as the printed media is to readers" -- but you've simply taken the effectiveness of print media advertising for granted.
Half of all advertising is wasted, the trouble is knowing which half (accredited to various figures)
First of all we have to measure effectiveness, how is that to be done? Cost efficiency, response rate, cost to sales ratio? There is a fellow on here who is certainly better qualified than I on these matters so I can say little more. However, once we have decided how to go about doing it we can try to apply the method to various media, and we all know that companies will be spending millions on doing just this. Unfortunately though they tend to keep that sort of information to themselves and it's bound to vary over different sectors and product types anyway. So let's consider what we can see; the printed media has suffered a decline but is still with us, without going back to the link I think the Daily Mail had suffered something like a 15% decrease in sales over the last four years. But by how much has online viewing increased over the same period? Are the two figures proportional? Does web browsing displace print reading (not just newspapers) in a linear fashion? We can't say for certain but it's interesting to note that printed media still attracts advertising revenue, maybe not as much, but it's still substantial so those companies that have invested large sums in quantifying the effect of their advertising spend would appear to be confident of printed medias effectiveness.
Hacking claims made against Mirror Group: Ruling extends scandal further beyond News International
The tabloids are as bad as each other and even that self acclaimed pillar of probity, the Daily Mail, is hardly innocent either. However, there is a considerable gulf between a few corrupt and immoral journo's listening in to mobile phone calls (which is quite wrong, make no mistake) and the wholesale harvesting of personal information from sites designed to extract as much detail on users lives as possible. At least the papers were punished whereas the websites carry on regardless mainly because they are of great use to various governments. To try and compare the two in an attempt to justify what FB is doing is a little desperate to say the least.
