I currently work part time for a custom e-commerce company, so I feel I have to put in my 2.2 cents here.
Since our e-commerce systems are based on JSP/Tomcat, IBM DB2, JScript and HTML, there can be just a few things which go wrong, particularly if the server's acting up, so we have a dedicated team of admins and helpdesk people to keep an eye on the server and continually maintain its quality.
At the same time, we find that clients generally need hand holding to a certain degree (from just a little bit to everything being done for them). The software's designed to be easy to use so that anyone can use them, yet most people still find they need some help, so that's where the helpdesk people come in.
So yes, you usually will need to provide some amount of tech support to end users - how much, of course, depends on how quickly they learn