My answer:
Photoshop Elements has had the Magic Selection Brush since version 4. When used in mask mode instead of the default selection mode, this tool is basically the same as quick mask mode in Photoshop.
To switch the tool to mask mode, select the tool from the toolbox, then look for the "Mode" menu in the options bar. Pull the menu down and choose "mask" instead of "selection." You can also make selections with other tools, then switch to the Magic Selection Brush to see the selection as a mask.
Later, in Photoshop Elements 6, the Quick Selection Tool and Refine Edge dialog were included. The refine edge dialog also provides a way for a selection to be viewed as a mask, and also provides smooth, feather, and contract/expand controls for fine-tuning the original selection.
Remember, Photoshop Elements also includes adjustment layers which operate using a mask to make selective corrections, as demonstrated in this tutorial.
So, although Photoshop Elements does not have a quick mask mode which functions exactly the same as the feature in Photoshop, I believe these tools more than make up for the absence of quick mask in Photoshop Elements.
Also see:
• Magic Selection Brush in Photoshop Elements 4 and Up
• Quick Selection Tool and Refine Edge in Photoshop Elements 6 and Up
• Selective Correction with Adjustment Layers and Masks
• Adobe Photoshop vs. Photoshop Elements - A Comparison
• Add-ons and Tools for Enhancing Photoshop Elements