I think this is very good feature because lot of end user do not know about SharePoint list item limitations. End users may be keep on adding item to list that will hit performance of the SharePoint server. To avoid these kind of problems MS introduced this new feature called List Threshold and Throttling in SharePoint 2010.
In SharePoint 2007(MOSS) the max items that can be returned by a list view was about 2000 items and any query over that number can result in low performance and load on the server. but in SharePoint 2010 the lists has been optimized to support millions of items and provide SharePoint Administrators control over how many items are being retrieved from the lists at a time using User Interface or Object Model.
Here is the code snippet which will insert 10000 items .
The below screenshot shows that when a list has items mover than the threshold (Default 5000).
you can get above page clicking the list settings as shown below.
Here is the list of various Throttling settings we can set.