Deletion policy is currently an ongoing issue of discussion here on ProductWiki and currently undertaken by administrators only. However, this doesn't stop you from helping to identify spam, vandalism and products which have questionable merit.
If you happen to come across spam, SEO attempts or vandalism that hasn't been identified by administrators (these are generally deleted within 24 hours) - feel free to simply add the word DELETE to the product's Product Line attribute. This will bring the spam to our attention through the products nominated for deletion list, and should get it deleted rather quickly! Thanks!
If you identify spam, SEO attempts or vandalism within the description, link or comment sections of genuine products also feel free to alert administrators by adding a note to the talk page of that product.
Products with questionable merit
If you believe a product you have found does not fit our accepted definition of what a product should be (definition pending), feel free to add the word DELETE to the product's Product Line attribute. This will bring the product to our attention - as well as the attention of other concerned ProductWiki members - through the products nominated for deletion list. You may also add the 'call for product deletion' notice template to the product's description. This will bring the specific issue you're having to the attention of other passing members who view the product.