My thoughts on this, living in the UK:
Why is this not as prominent as Caylee Anthony's case ?
Caylee's case also happened during a rather slow news period, but even so, it was obvious to most people that Casey Anthony's story was suspect from the get go. The McCanns, on the other hand, had the advantage of the very first night--"They've taken her!" dramatic scenario.
A single parent's child disappearing--everyone automatically suspects the parent or the parent's partner, and statistically for good cause. However, the McCanns were an upper middle class couple, well educated, attractive, who were just vacationing together as a family when tragedy struck. (According to their script.) Who wouldn't feel sorry for them and send a check to the fund to find her?
Madeleine's case was pretty big in Europe, because of where the crime occurred, the McCann's subsequent globetrotting and M's pictures...which everyone is understandably sentimental about (just as with Caylee)...
Why do people tend to think the McCanns innocent but ready to as is said over in the USA *fry* Casey?
See above...Casey wasn't smart enough to hide or have lawyers hide her text messages where she referred to Caylee as the "brat." Madeleine's parents had all that deleted or suppressed.
I am with the OP, there are many who think the McC's know more than they are letting on and there are many conspiracy theories. It has been easier, somehow, for the McC's to 'silence' the media, and sue them, than it might have been in Casey's case, as the States is obviously huge, with lots of local and national papers, etc - We have only a few, so it's probably easier for the McC's legal folk to stop anything they feel is anti-McC... There has also been a lot of stuff put out there in the media about Casey (the 'phone calls, the prison visits, etc), making it easier to condemn Casey as is probably correct - We have not had the same 'access' with the McCann's, but we do wonder why Social Services never questioned them about their clear and reckless abandonment of all the children, while they were out socialising.
In Australia everyone knows about missing Madeleine but no one has really heard of Caylee Anthony or Casey Anthony - why do you think that is ?
I think Australia is still pretty close to the UK (strong linked history, families, immigration, emigration, and so on), and vice versa, whereas the USA is clearly longer independent, if you know what I mean.
America is also huge, sorry for stating the obvious, so for the UK or Australian press to cover all the US's newsworthy stories, including Caylee's would be nearly impossible and expensive for them...
Does money buy you silence ? ) Probably!
Does money buy you freedom ? )