I think a bigger issue is what purpose we want our possessions to serve. For example, in the U.S. we have warped view of the purpose of cars. Their purpose is simple - transport us from point A to point B safely, but in U.S., we tend to view vehicles as status symbols and we are more concerned with the look of the vehicle and all the features more so than it's function! The same could be said of a place to live. What is the purpose of a house? To provide shelter for a family. When we stray too far beyond this simple purpose and begin to desire oppulent homes with amenities that we don't really need, but simply desire things because of greed, then yes, I think it is sin. For example, does a family of 2 or 3 need more than 2 or 3 bedrooms? Does a newly graduated person need a home with a swimming pool and a gameroom? It is imperative that the Christian live within his/her means and be content with God's provision.
To an extent, Andrew, we can agree. However, we cannot possibly know the motive of every person who buys that which they don't
need. We do this all the time. We could go buy a bag of beans at wal-mart and put them in the crock pot each night for food the next day, but we don't
always do that. Why? Because we like variation in tastes, etc. that we don't
need. But we certainly wouldn't argue that it's wrong to experience those other tastes. So we go out for dinner, or we have Tex-Mex one night, and a steak the next. That doesn't make us greedy (necessarily), just as I would argue that a 3 member family purchasing a 6 bedroom home with pool and other needless amenities is doing so out of greed (necessarily). The mark of a Christian is what do you do with what you have. Since you have a home with more bedrooms than "needed," do you provide a place to stay to brethren in need? Are you giving generously to the church as God has generously given to you? Those kinds of things. We have to be careful not to make presumptions about other folks according to their worldly goods and, instead, place the best construction on the matter. If people are outspending their means and gaining debt, well, that's something with which the elders should deal.