We did a guest post for Frooition on the subject of why eCommerce companies need a WMS! Excerpt:
Acquiring and maintaining accurate inventory quantities is a problem common to most all eCommerce retailers – from overselling (aka out of stocks, aka stockouts), mis-picks, and mis-ships, to forgotten stock sitting on a shelf, not even listed for sale. An inventory and warehouse management system helps to greatly reduce those inventory issues, and many other problems online retailers face. Check the post out, and the rest of Frooition's awesome eCommerce blog while you're there!