As a Christmas gift, a good friend of mine received the complete first season of Star Trek: The Next Generation. We have been watching copiously since then. The first episode, "Encounter at Farpoint", was originally aired in 1987. Twenty years later, some of Roddenberry's technical oversights add another level of amusement to the show. I am no Trekker. Please correct oversights on my part.
In the future, there are no firewalls.
It seems like anyone can take control of the Enterprise's systems. In the very first episodes, Q interferes with their computers. In the third episode, Wesley takes control of the ship from main engineering. In the fifth episode, Portal, an ancient leader (guardian of the Tkon Empire), drains both the Enterprise and a Ferengi vessel of it power. Things continue this way for the rest of the season, and from what I remember of the other seasons, don't seem to get much better. Word of advice to the Federation: consider Norton Internet Security.
Security Systems are SO overrated
As far as I can tell, there are very few internal security systems on the Enterprise that are designed for dealing with violent threats. In the episode "DataLore", no one is alerted when Lore disables Data and takes his place. You would think a computer as advanced as the Enterprise's would be able to keep track of its officers. In episode "11001001", the Bynars take over the whole ship and seal off the bridge. In the episode "Lonely Among Us", the Enterprise is charged with the task of taking delegates from two worlds to a peace meeting. By the end of this episode, the delegates are hunting each other in the halls with stun guns and nets. Roddenberry's significantly less popular show, Andromeda, made use of internal security systems (although mostly they were used against the crew in freak accidents...). Too bad Andromeda failed to have compelling characters, believable lines, or half-way decent plot lines. Oh well.
Spacesuits are overrated too.
On of the first things the away team always does is break out their tricorders and scan the environment. Their scans always inevitably tell them it is safe to be flouncing around whatever planet they are on. But what if it wasn't? They very rarely wear protective gear. They beam down to strange planets, abandoned and disabled starships and hostile territory without so much as a helmet or a phaser-proof vest. Not only do they beam over unprotected, they beam back unprotected too, without so much as a quick decontamination. In the second episode of ST:TNG, "The Naked Now", the Enterprise is sent to see what is going on at SS Tsiolkovsky. In this episode, Geordi beams back carrying with him the deadly infectious virus that killed the crew of the Tsiolkovsky, infecting most of the crew.
Thankfully, those kooky Federation engineers were not too keen on security, otherwise Star Trek: The Next Generation would have been an awfully boring series.