I remember reading some e-commerce usability studies and on payment pages, people felt better when, next to images or names of payment options, they saw something that "looked secure" such as padlock icons and whatnot.
It's silly but then we never said human psychology was rational or actually bothered to see if those symbols actually mean anything.
Many of our e-commerce clients do have trusted seals on their home pages but those actually mean a link to their chamber of commerce (KvK) numbers and those pages can show things like number of complaints or where to contact to file a complaint, which doesn't sound much like these other "trust" things.
example upper right: http://www.fonq.be and http://www.fonq.de (different links because different countries) and 2 customers have link-images to http://www.unizo.be/ecommercelabel/labeldragers.jsp (which is more like an organisation linked to consumers' groups).
It might be a European thing, or it might be some other reason. Most of our clients are small but the fonq one is actually kinda big and old, no they really don't have a need to "prove" themselves. Maybe some SEO-er told them they're better off with it