I think Onhwy61 nailed it. LCD's are simply better in most rooms because most LCD's are non-reflective and, because of this, most stores will push the average joe toward LCD because it will work better in the average room. LCD displays are much better than they used to be and the divide between plasma and LCD has diminished greatly, IMHO. I have a Samsung LCD and with a good source (HDTV/HDDVD/Blu-ray), its an excellent display.
Why are LCDs more popular than plasma?
I have a rough time seeing differences in picture quality between brands and models, but the difference between plasma and LCD are overt even to me. When I go to bestbuy, fry's, etc. and gaze at their displays of flatpannels, plasma televisions just look beautiful, despite the reflections, while LCDs just remind me of working on my laptop. Is there more merit to the quality of LCD than I observe or is there some other reason LCDs outnumber plasmas?