Years back when I was more involved with cat rescue, I remember often picking up a cat and trying to analyze the personality in the time that we had to do so. One little waif was purring and wanted to snuggle the minute I picked him up. I held him close and said to the other 'rescuer' next to me, "Looks like this little guy got the 'friendly' gene. She just looked at me like I had three heads. "The friendly gene, you know, from the dad." Did you know that kittens can have the gene from the tom that gives it the 'boldness' it needs to survive this world? Paternity plays a major genetic role in a cat's boldness, which also includes their friendliness.
Studies performed in 1995 in England show that a father cat that investigated new objects and people without hesitation produced kittens that did the same. So, I always looked for cats that had the 'friendly' gene so I could tell the prospective new owner that the little fella got that from its' dad. It always raised some eyebrows. :) The not-so-friendly cats would be adopted to more experienced cat-lovers so that they would have the patience to work with these scared ones.
Cat-tip-for-the-day - picking a kitten
If you are picking a kitten from a litter to 'call your own' you are best to leave the kitten with the mother for 12 weeks. These kittens have been studied and it is shown that they are more likely to be friendly with other cats in the future.