I agree with r_poster. It's often said that it's best to close your credit acounts in order to approve your attractiveness to lenders. Having worked in credit a litle bit, I think that the negative effect that would have on your debt/potential debt ratio is the bigger worry. (MSN actually had an aricle on this about a while back). You can have one billion dollars in available credit, and having a million dollars of debt in that situation is not a terrible thing (I believe 20% or lower is the ideal ratio). This may belong on the other thread, but I have heard that 640 or thereabouts is the lowest score one can have in order to be approved for a private loan, but that's just what I'v heard.
You ask a really good question about whether it matters if you carry the same credit card balance on one or multiple cards. The exact scoring system of FICO is kind of mystery (I once had the percentage breakdown of each factor- I'll try to find it and post it in a couple of days), so I'm going on a rumor here. I've heard that there is an additional penalty to your score if you approach the credit limit on a credit card. So it might be better to have a $1,000 balance on each of two credit cards that have $2,000 credit limits, than to have one at zero and the other at $2,000. Again, not sure about this last part.