I heard several times that two SNPs, that have at least 1'000 nucleotides between them, can be seen as 'unlinked' due to frequent recombination events. I also once saw a paper showing a graph "degree of linkage vs. genetic distance". Unfortunately I can't remember which paper it was. Does anyone know where this number (1000) comes from?
PS: I'm aware that this topic is much more complex, especially if you are interested selective sweeps.