Wikipedia freefall is the gradual degradation of efficiency that occurs when you try to research a topic on Wikipedia.
Wikipedia is one of the internet's greatest blessings, and its biggest curse.
The first destination for anyone seeking a grounded understanding on any topic imaginable, from Ancient Greek architecture to a full episode list of DuckTales, Wikipedia litters its articles with hyperlinks for ease of progression through its infinite maze of information.
But beware! Wikipedia is strewn with detours, distractions and traps. For each innocent-looking blue-underlined word seduces you with its own siren song: "Would you like to know more?" If you have ever begun to research the Australian Constitution and found that you have spent the last three hours reading about Milhouse from The Simpsons, then you are a victim of Wikipedia freefall - the hapless descent through Wikipedia from topics relevant to your research into the realm of idle self-interested procrastination.
A psychological explanation
When faced with the threat of actually doing serious work, the human brain is equipped with an emergency response system that taps into hitherto inaccessible regions of the mind to scan every aspect of your life in a desperate attempt to find some reason to avoid doing said work.
If it becomes apparent, for example, that you really need to start work on a project for which the deadline is rapidly approaching, the brain will go into overdrive, automatically listing the alternative options. You might suddenly remember that you are out of milk, and should you decide to obtain some, your mind will further suggest that this is as good a time as any to undertake your full week's grocery shopping.
Should the alternatives run dry, the brain will go to increasingly desperate measures to locate possible avenues of procrastination. In this case, you may be struck with overwhelming nostalgia for a cartoon you used to watch when you were nine, and as such you may be driven to Youtube to rewatch its opening sequence, and the opening sequences of every television show you watched during your teenage years.
Wikipedia provides a service to maximise the productivity of your brain's procrastination protocol. Every paragraph in any article contains no fewer than three hyperlinks that serve as "exit points" for speedy escape from whatever you are trying to learn about. It is guaranteed that almost every one of these links will become more appealing to you than whatever you are attempting to research. One should never underestimate the brain's desire to absorb information about whatever is not important for it to learn.