First, Barclay seems to be able to just use the holo-deck whenever he pleases. I don't know if it's an officer's privilege or what but he gets the urge and hops in a holodeck. Given the number of people on the ship I'd have imagined holo-deck time being rationed or at the very least scheduled. Barclay just hopping in whenever he pleases seems a bit odd in hindsight.
Second, no bloody locks. When Riker, Troi, and Geordi go looking for Barclay they just walk right into the holodeck. No over rides, no door chimes, nothing. They just walk right in. If you're climbing El-Capitan or whitewater rafting or just playing chess with Einstein I can see you not really caring about whether or not the door's locked. When goofing off with ridiculous facsimiles of your superior officers and boning the ship's councilor I figured you might want to not just let people walk in.
Which leads to the big question. When Riker, Troi, and Geordi enter the holo-deck they run into their doubles. Riker gets pissed because the holo him is about 5' nothin and goes to delete the program. Troi stops him with her usual depth as a councilor (none) then Riker rebuts with something along the lines of, "This is against the regs." Which would make some sense. Barclay had quite obviously created exact duplicates of Riker, Picard, Data, Geordi, Deanna, and Crusher. However Geordi stops him with, "Actually sir, no he's not." Riker doesn't push it, he just accepts Geordi's pronouncement with, "Well there should be a reg against it." Immediately afterward they run into Barclay's copy of Deanna and she gets pissed. Now mind you Barclay was just using the male copies for ego stroking and as digital whipping boys. He was using Deanna's clone as a virtual blow up doll. However, according to Geordi him using their exact physical representations broke no regulation. It was, according to the closest thing TNG had to a holodeck expert, perfectly legal. This can't have been something new. Imagine if the technology was developed today, how long do you think it would be before some had created a "Bone Angelina Jolie," holo program? Which brings me to the question, what do ya'll think about that?
To me it just seems odd that you could create an exact duplicate of someone and then use their likeness however you please. Mind you this isn't entirely without precedent. There's a cottage industry built up around faking nude pictures of female celebrities or writing questionable stories about them. You could see this as taking it to the next level. So while I can see some precedent for allowing it this goes to a whole new level in that it's not faking anything anymore. Barclay created PERFECT replications of his crewmate's physical bodies. I'm assuming from something like sensor scans or transporter records. It's one thing to paste Angelina Jolie's face on some porn star's body. It's another to create and exact duplicate of her physical form that you can interact with. It just struck me as a very odd thing to have happen.