There's been a fair amount attention to the work of Professor Simon Blackburn on lust. He suggests that it should be a virtue, not a vice. Clearly provocative books sell more copies, and I haven't read it so I don't want to be too rude about it.
I think that it's important that lust should be seen as a sin. Most of the interest has been in sexual lust (no surprise there, really), but there is also lust for power, money, status and lust for material goods.
We need to destinguish between lust and desire. Desires are good and natural. We desire to be intimate with people, we desire to be cherished and valued. We desire to be comfortable, secure and safe. Lust is not just a strong desire, it is a perverted desire. So the desire for intimacy becomes a lust to possess a person. The desire to be cherished becomes a lust to be more important than another. And so on. Desire can and must be very strong, but they must also be disciplined. One can desire God - the Psalmist knows this very well - and this is a desire, a longing, that involves the whole person.
According to the BBC story, Blackburn "points out that thirst is not criticised although it can lead to drunkenness and in the same way lust should not be condemned just because it can get out of hand". This seems to me to miss the point entirely. Lust is precisely when a thirst, a desire, has got 'out of hand'. We suffer immensely because we have lost the vocabulary to distinguish between lust and desire. 'Desire' has become almost exclusively associated with sex, and sex as lust at that. 'Lust', it seems, is now being flattened out into a generic desire.
Of course, mentioning that one can desire God prompts the question of whether one can lust after God. I think that we can, and do. Lusting after God leads to thinking that we can (or, worse, do) possess God. That God will back up our stance entirely against another. More subtly, lust for God is a form of idolatry (an idolatry of religion perhaps!).
I think Pope Gregory knew what he was doing when he compiled the list of seven deadly sins!