I believe that the biggest issue with caffeine is if you have high blood pressure as it can exacerbate this. So if you have a family history of high blood pressure/pre-eclampsia, I would cut it out entirely. Otherwise 1-2 cups a day seems to be acceptable.
Unlike alcohol, where is proven negative impact on the development of the baby's brain and body (eg. fetal alcohol syndrome), or soft cheese which poses a listeria risk - which breeds like wild-fire in the placenta and puts the baby at immediate risk - the risks with caffeine seem a lot less.
I would treat energy drinks with caution as they often contain other additives such as guarana (which is mostly caffiene anyway) and taurine (no idea what this does). There are also some vitamins that should be limited during pregnancy (A?) which could be added.