Hi Elynor,
Yep, this has been happening for a little while now - and to also add something else you may no tbe aware of, there is a 'limited' life of printers on the market nowadays - there are 'techy' ways to get around the issue some easier than others. It's been a fair while since I've looked up info on it, but I remember something about ink tanks within the printer mechanism itself and an overflow tank? i think - basically once the printer detects thats full, it doesn't 'work' anymore - out you must go to buy a new one. Heavy users may find that takes anything from a few months to maybe just under a year - the manufacturers will say its becuase it keeps the quality output consistent, but cynics will say it's a ruse to limit useful life and thus making a consumer have to go out and buy another unit...
Like 'any' company - it's out to make profits, the threat of grey imports, fakes, and copies from other areas which can reduce profitability - measure like this are taken. It's happened with DVD's for ages, moved onto new digital media as well and hardware too. I see the 'business' aspect of it - but away from my 'business' i'm also a consumer and it is infuriating.
I think other manufacturers do this region of cartidges control as well - not just HP..
Cheers! DtM! West London & Slough UK!