The Spaghetti Strategy is when a player makes a large number of accusations against many different players, waiting to see which of them will actually be successful at arousing people's suspicions. The player then follows up with that particular suspicion, forgoing the rest they have just made. This is often seen as an effective scum strategy, since it allows them to appear like they are contributing and scumhunting, when in reality this appearance is all they care for - by pursuing the most popular and/or least offensive case, they avoid people scrutinizing their own behavior while concentrating on the behavior of others.
This gets its name from the image of someone flinging wet noodles at a wall; throwing one or two and they will simply fall down, but if you throw enough, eventually one will stick. This tells you that the noodles are ready, but that is beyond the scope of the metaphor.
Who came up with this term is a mystery lost in the sands of time. I think it was Authorman.
Be careful with this term; a player simply posting a lot of suspicions is not necessarily performing a Spaghetti Strategy, nor is the player pursuing the best of those suspicions (would you prefer they follow the worse ones?). A player is committing the Strategy when they post a bunch of cases and only pursue one of them solely because others seemed to like it; anything else is, arguably, not scummy behavior, and just a player being scumhunting and practical at the same time.