The hypothesis goes like this:

The two forms of memory, "lossless" and "lossy" have complementary function. Lossless memory tends to produce individuals who are more concrete (because they can recall random data associated with individual objects/situations), less creative and less abstract, while lossy memory tends to produce those who are better at synthesis, creativity and abstract thought (but who can't remember a name 4 hours later).

The reasoning goes that those of us with "lossy" memories tend to store things as rules/assumptions with exceptions. The individual tends to systematise and rationalise what's around them into rules and stories. They can remember remarkable exceptions well, but normal or expected patterns don't stick particularly well. Result of that is that ideas tend to get bound to one another (seeing patterns between things, pulling up other related ideas), which effect, if it gets too intense might get you eaten by a tiger, but which also might let you dream up a way to trap the tiger and eliminate the threat altogether.

Or so I tell myself to make it seem like there's some trade-off for the forgetfulness...