Ok,

let`s assume you can acquire a clone from somebody. Could you use that clone as an material link?

In Streetmagic it says: If the target is a living being, the material link is a tissue sample. (page 29)

A clone grown from the persons tissue sample should be regarded as a tissue sample of that person, so if you could grow a clone from someone without him knowing you would have an everlasting material link, right?

Am I missing something or should this work?

Ok, it would be quite expensive to store the clone somewhere and the original person might spend a lot of time and money to track you down when he realizes what`s going on (which still should take some time). But it would open up a lot of (funny) options to use someone as your puppet or e.g. for blackmailing purposes...imagine you`d just cast from time to time a nice "Dream" via ritual spellcasting as a reminder of your monthly payment instead of contacting the person by other means...would be fun

well, if it does work the spell will point to both clone and other guy . . but you know where the clone is, so you can find the other guy . .
would that work the other way around too?
if you can afford it, scatter some clones of yourself around the world and watch every mage trying to pinpoint you explode from frustration? ^^

Well, considering that you can change your aura...
...Then it makes sense that although a clone is physically identical to the original, the aura is not.

So a clone would actually have a different aura.

Well, the question is: has a clone with an underdeveloped brain (see page 53 Augmentation) that cannot even keep him alive an aura? In the core rules it says every living being has an aura...I guess one has to count a clone (even brainless) as a living being...

Nevertheless it still should help to put the clone in a magical secured area (FAB walls and that kind of stuff) to avoid targeting the clone with the spell instead of the original person.

Genetically identical does not mean aura-ly identical.