* Running any website with user-contributed content. Spam is just everywhere nowadays, and you cannot publish a simple hiscore list for your game anymore withou

* Running any website with user-contributed content. Spam is just everywhere nowadays, and you cannot publish a simple hiscore list for your game anymore without some kind of anti-spam measures, otherwise the spammers find it astonishingly fast and flood it with spam, even if it doesn't allow any clickable links * Thinking about it some more, everything related to security. Back in the days, the whole Internet wasn't port-scanned for known vulnerable services multiple times a day, and you could get much further with less refined security practices. * Drawing things on screen. Back in the days of DOS and QBasic, it was just a single line of code to put the screen into a different mode and start to paint lines and rectangles on it, placing text at certain coordinates. Now you have to have a GUI (though canvas elements in web pages make it a bit simpler again; still not quite as simple as in the 80s/90s) * Getting access to a particular memory location, without layers and layers of virtualization in between