Dell has been reported as a 10% customer in the SEC filed quarterly reports for a long time. For the past couple quarters Dell was the only 10% customer. Take a look at the Ten Percent Partners on unclever.com. (Not updated for Q3 2008)
Your scepticism is understandable, but I think you can put it aside regarding this issue.
There's always a reason: I imagine Dell doesn't want it highlighted that it is supporting an important supplier. Who knows what the world would be coming to if everyone wanted a bail-out.