<p>I'm writing a pretty straightforward <code>e-commerce app</code> in <strong>asp.net</strong>, do I need to use transactions in my stored procedures?</p>

<p>Read/Write ratio is about 9:1</p>

Many people ask - do I need transactions? Why do I need them? When to use them?
The answer is simple: use them all the time, unless you have a very good reason not to (for instance, don't use atomic transactions for "long running activities" between businesses). The default should always be yes. You are in doubt? - use transactions.
Why are transactions beneficial? They help you deal with crashes, failures, data consistency, error handling, they help you write simpler code etc. And the list of benefits will continue to grow with time.
Here is some more info from
http://blogs.msdn.com/florinlazar/