In my view there can be many types and many levels of lust.

When you see something in the store (like a computer etc) and you want it, to me that is a version of lust ... so materialistic

Then you can lust after someone ... sexual.

Since we seem to be talking about sexual lust I think it is alright as long and both parties are interested, but I dont think you should follow your lust if you are involved with someone and your lust isnt for them.

But as I like to say, its alright to look and admire but dont touch.