i think tho with something like xboxgamestore.co.uk, altho it is using a trademark, microsoft would be less likely to go after you as it is selling a product they dont sell directly themselves. - if microsoft goes onto your site and sees lots of crosses over there products they will also shut you down quicker.
where as if you did argosstore.co.uk they would go after you quicker becuase while your a affi of them they make less money than had the user gone direct to the argos.co.uk store. - i also see getting ranked above argos as a problem myself but your
seo might be very good.
in short i think it depends on if the tm is a store that sells direct or not and if it is a brand name like lg plasma's then im sure that lg might tern a blind eye at it. .....tho i might be wrong