I have a large number of product based websites and I just discovered that more than half of them are sandboxed. If I search with "site:url" they can't be found. I haven't done a lot of backlinking to them, some of them only a directory submit and they have 5-10 backlinks according to yahoo site explorer and they are a couple of months old. I really don't get it, I understand why some of them got sandboxed (a lot of sb & xrumer links) but most of them don't make any sense. Could it be that they are all on the same hosting account?