WARNING: Be careful when keeping rice warm. One of the commonest causes of food poisoning (actually THE commonest according to the food hygiene course I did) is rice kept warm in restaurants .
Warm rice provides the perfect environment for staphlococus, a nasty little bug that lives in the grooves in your fingerprints (and just about everywhere else). Fortunately it's not as serious as listeria or salmonella; normal symptoms are 24 hour D+V.
The problem is more severe in catering environments because food is more likely to have been handled by more people and because of the larger quantites involved. Leaving rice around your kitchen for a couple of days and then eating it is a bad idea though, unless you want to get intimately accquainted with your toilet.
This has been an Everything Public Service Announcement brought to you by PaulM.
See also Bacillus cereus for more detailed info on a bacteria behind rice based food poisoning.