POS's are an interesting thing. The bubble is a shield of invulnerability which is much like a bathysphere - you can see the horrific fish of the deep probing around in the nightly abyss but you are safe and warm inside the impervious glass, shining your lights outside.
You can be assured that the only people looking in on you are doing so from weak, cloaky ships which cannot possibly survive the defences you have assiduously piled higher and deeper above and below your crystal ball of tranquility. Thus you can take certain liberties within the overwhelming firepower of your POS defences. Anything larger and cloakier is frankly too expensive to throw away on ganking, for example, let me list the shit I have ganked (and what I have lost doing it).
But first, by way of introduction to the subject, how we come to this topic: last night I pprobed into a C2 wormhole. Cheetah at the POS, idle. Eventually a capsule turns up on d-scan, so i check it out. I discover the capsule is for a pilot not belonging to the POS owner, and is idle outside the POS bubble. I place my scout 10km away from the capsule, in line with a moon, warp TF in his brand new experimental Scythe Fleet Issue to the scout at 30km, lock and pop, and scoot to another planet immediately, having taken shield damage but not being scrammed by the warp dissy.
Highsec Express, One Ticket Please
The key to this behaviour is that POS guns take a certain length of time to lock you, depending on sig radius and gun scan resolution. You can loot wrecks and scoop corpses in a covops before the dissies lock you, alpha stuff with, eg, a Naga, and pod people who are too dumb or alt-like to be given the POS password and must cool their heels outside. (and why no bomber? because bombing a pod is actually harder than alphaing it).
So. To the list of shennanigans;
Sudden Buggery engaged 3 RR Domis under the guns of a deathstar, destroying all three for no loss. They were visitors chilling under the POS gun protection - their mates had set the POS to pussy-mode so they wouldn't get shot.
I dropped a gank Cyclone on a Deimos and a Brutix playing "test my gank" outside their POS. Ganked the Deimos, nearly killed the Brutix as well, before the guns popped me.
Dropped 3 BC's on 2 Tengus and a Drake doing the same, 200km above their POS. Killed a Drake and a Tengu, and scooted 50km up to break dissy. No losses. Again, you may think you are safe but remember, it takes a while for the guns to lock your enemy, you are all being dickheads and your tanks are probably not 100% super-tough, and by the time you are dead they are already well on a steam (1.5km/s) so if your POS takes 30s to kill a Cyclone, it's not going to protect you. Also, I'll gladly exchange a T1 battlecruiser for a shot at 2 Tengus.
Alpha'd various haulers dropping or picking up POS guns, including T2 haulers; you merely need to set up a scout off the hauler's destination and warp a Tornado, naga, etc in at 70km, align out while locking the prey, and hope you alpha him. Never do this in an Orca; I ganked an Orca with my now-defunct alt Sparkletta who was scooping the last of his POS modules, after clloaking a Domi off the POS guns and waiting for him to warp down onto them.
Never store anything in cans outside your POS bubble. You will find some nutcase will drop a gang of RR BS onto your Megathron as you are dicking around with your can full of loot, and then slowboat out of the POS gun range and dissy range while trolol'ing in Local.
Launching probes from a 350km safe atop your POS? Well, you remember that the Tengu dropped into a safespot in system that prompts you to go to the safespot 350km above your POS to launch your combat probes? Yeah, it was all bait and now your Anathema is tackled. Oh, and guess that the rescue party who warps up to save it? They meet a rape gang coming from the K162 which just spawned. Bzzzt. Bit too far from the POS guns. (In this case, I had the POS, and the 350km safespot, saved from a vvisit 9 months earlier. Do not assume no one knows your secrets!)
What have we learned today? POS bubbles are a fun toy. POS guns are not an effective deterrent if you leave someone an angle and a juicy target to have a run at. And that involves doing the maths on, eg, what does it take to gank my ship even if everyone who comes to do it dies? Hulk vs Catalysts are welll known from highsec, yet you see people chilling outside POS bubbles in Hulks all the time.