On its own, the word for 'covet' (chamad) here just means desire, and isn't a bad thing. What makes the coveting evil is the fact that it's about someone else's things. Translation: it doesn't belong to you but you want it anyway. So why is it bad to see your friend with the newest PhonePadTechlookingthing and fall over yourself to get one too? Well, it's not particularly honouring to them. It's a missed opportunity to 'rejoice with those who rejoice' (Romans 12:15 NIV), and it's really quite self-centred.
And in the 'you shall not covet your neighbour's wife' (Exodus 20:17 NIV) part of the verse, dishonouring becomes dehumanising. Sometimes we treat people as bodies to lust after or wish we had instead of our own. Or how about that one person who seems to have it all perfect? And you just wish you could be them? - same: not good for anyone.
Coveting people or their things (and yes, if it is in a shop, it is still coveting...) becomes a worship-full experience and then we're, well, 'worship-empty' when we go before God. We have no space left for Him, because we tried to feed this hunger within ourselves with the wrong stuff or people. If we get what we wanted so desperately we still wouldn't be satisfied. We'd want more. That desire to be filled is a Jesus-shaped space only He can actually, truly fill.
So what now? The next (affordable - chocolate, CD, lipstick, whatever) thing that you find yourself 'chamad'-ing in a shop... buy it. Then give it away to someone who you know will like it.
Soulfood : Acts 27-28, Matt 5:27-37, Ps 35, Prov 11:19-21