When you go with more custom characters, all get their tadpole dream and power, no matter if they ever used it or not. You can also cheeze your way out of this problem, if you wish to be a little asshole ... and use your companions, they use the tadpole to dominate some goblin, you get your super tadpole power, and then you can be pissed off at them, that they were not careful enough. I especialy enjoy tormenting Shadowheart like this. :3
I have definitely seen it with the full custom party but was wondering if it made a difference with multiple actual players. Personally I think it should be allowed for someone to get tadpole powers and the rest to not know, hence why I think they are using the bloody thing as an excuse for everyone knowing everything. Would make no sense otherwise for someone to blab to the rest of the party that they gave in.