PS3 "resume" function - hit & miss

[nightcrawler]

What's the deal with trying to resume play on a Blu-ray disc on the PS3? Some discs will resume play where you left off (some even after removing disc from the PS3 and reinserting), others will start up from the beginning again. Is there a setting I haven't changed, or is this normal and determined by whichever studio released the disc? Also is it isolated to the PS3, or are all BD players like this? It just seems hit & miss to me. Whenever I need a toilet or drink break during a movie I always hit pause now instead of stop. It's no biggie, just a little annoying - especially if you want to continue watching something another day.