Estimated calories burned?

How does everyone feel about the estimated calories burned? Do you believe what MFP, Map My Fitness, or Map My Run say about it? Do you think its over? Under? By how much?
I often feel like its over estimated my calorie expenditure.
I don't follow the theory that is as simple as calories in - calories out (but that's another topic) and I don't usually 'eat' my exercise calories, but I'm curious what y'all thing about the estimates.
Phoebe