Hmmm a slight difference here between T1 and T2. But theres an underlying problem with baked potatoes themselves. Boiled potatoes (depending on variety) can have a GI of around 80. Baked potatoes are well over 100 (up to 158). So would you be better just eating the contents of the sugar bowl? Quite possibly yes.
For those finding problems with the timing of insulin for baked spuds, thats because of the high GI. Baked potatoes hit the BG hard and fast. Butter and other fats will slow it down slightly but its still likely to throw off your calculations with regard to timing. Slower GI foods are easier to plan for. Doesn't mean they should be on a banned list, but its one to be careful about. As usual, managing the quantity (GL) and speed (GI) of carbs can mean better control.
As for the T2 viewpoint, I have very few banned foods, but baked spuds are in there along with cereal bars. I tend to start a meal around 5mmol/l. My one and only incident with a baked potato shot me up to 12, followed by a crash to below 4 a couple of hours later.
Despite the dieticians' one-size-fits-all-whether-you-have-diabetes-or-not diet sheets, having a lot of starchy carbs with every meal is not actually mandatory - so long as you do not fill the gap on the plate with pure lard. Its just a question of finding alternatives which do not cause a problem - other veggies with less carb in them for example or benecol instead of butter.
So every T2 in particular should be aware of GI and GL. David Mendosa's site is as always a good place to start:
http://mendosa.com/gi.htm And of course its also important for T1s.
But for T2s in particular, the bottom line is how a particular combination of foods affects your body. And only your meter will tell you that. The important thing being to learn from the results and see where you can improve a particular meal the next time.