I do use the MyFitnessPal database, but I also check what it says. I suspect some users who create/amend the entries are overly optimistic about how few calories, carbs and fat are in certain products. That said I've also found entries with far too many calories when compared to the original packaging and similar products from other manufacturers.
The one thing I'm also wary of is meat where sometimes the calories on MFP are for raw and sometimes for cooked. It can be very confusing at times.