<p>I'm using the new ASP.Net ListView control to list database items that will be grouped together in sections based on one of their columns like so:</p>

<pre><code>region1
    store1
    store2
    store3
region2
    store4
region3
    store5
    store6
</code></pre>

<p>Is this possible to do with the ListView's GroupItemTemplate? Every example I have seen uses a static number of items per group, which won't work for me. Am I misunderstanding the purpose of the GroupItem?</p>

I haven't used GroupItemCount, but I have taken this example written up by
Matt Berseth
titled
Building a Grouping Grid with the ASP.NET 3.5 LinqDataSource and ListView Controls
and have grouped items by a key just like you want.
It involves using an outer and inner ListView control.  Works great, give it a try.