Every time I load up SO, I am faced with a bunch of questions in which I have neither interest nor expertise.
It would be really nice if SO noticed that my areas of interest are core audio / DSP, and my areas of expertise are algorithms / Maths, and show questions relevant to this.
Areas of interest can be calculated thus: say I browse a question tagged with 'badger' and 'fetish'. Then it would increment my 'badger' count and my 'fetish' count. If I am prone to looking up badger fetish related questions, it will soon show.
Areas of expertise can be calculated similarly, only they are added up differently: say I answer someone's question that is tagged 'walrus', and my answer gets three up votes. then my 'walrus' expertise increases by three.
Now how to display relevant questions? we could go by number of tags matched. so any question matching three tags would go before any question matching only two.
Put this maybe oversimplistic: I might match 1000 'iOS' tags, because that is such a common tag. but I might only match five ' core audio ' tags. but I would still want to view the ' core audio ' questions first, because that is a more exclusive and specific tag. to each tag would be weighted according to how rare/exclusive it is.
A question that matches one rare tag should preside over another that matches two common ones.