It is by design, however I think it would be a good idea to make it 'read only' for guests but still have a minimum posts requirement to list items there, that way you get more people viewing your items.

I am happy for mySandman people to post stuff for sale, what we don't want is people singing up just to sell their 1984 Corolla and then never return again. I believe the best way to prevent that is have people contribute to for the community by posting a few posts before being promoted into the Sales sections.