I used MFP for a few years back when I was actually flying and on the road a lot. I haven't used it for maybe the last year or so because I feel like I learned what I needed to about foods and don't really have to count any more. I'm sure that will change once I start going on the road more again. Things MFP taught me:
1. Exercise
2. Avoid pizza and ice cream (my guilty pleasures)
3. Exercise
4. Avoid the big chain restaurants: Applebees (by far the worst offender), Chili's, TGI Fridays, Pizza Hut, Buffalo Wild Wings, and surprisingly, Quiznos. (although some are actually pretty healthy, as long as you keep the portions in control: Chipotle and Red Lobster come to mind).
5. Exercise
6. Small changes make a big difference. Take the side salad, or even the mashed potatoes, over fries. On that salad, use a vinaigrette instead of ranch. Water > Soda. Stuff like that.
7. One that surprised me a bit: Avoid fast food and buy a big meal at a nice(r) restaurant. Buy your meal, get an appetizer and your drink of choice. Enjoy a bit of the free bread or chips. That way, when the actual meal comes, you're already filled up a bit. Portion the meal in two and set the larger part aside for leftovers. You'll eat much better than fast food (twice), enjoy a drink and a relaxing meal, and end up paying about the same, if not less.
8. Did I mention exercise?
I don't really use the exercise tracker, but the generic calories burned for a given activity seemed fairly worthless in that you could be well above or below those values depending on intensity. Better to calculate that effort with some other means and plug in the number.
MFP does adjust their calorie burns based on age and weight, and many exercises offer multiple intensities. Walking and running combined have something like 14 total intensities to choose from. Of course it'll never be perfect, but it does make for a good ballpark figure, which is all calorie counting ever is.
WTF does it need access to my contacts?????
Simple...they go by the idea that losing weight is easier when you have accountability or in a group setting, more so when you actually know said people. If someone in your contacts is also on MFP, it'll connect the two of you. I'm not saying that you shouldn't be leary of it, but it's a legitimate reason.