Future heavy discounting of un-themed links?

Google's director of tech.'s comments

[nuevojefe]

"To achieve high PageRank", Silverstein said "you want the expert sites in your market linking to you and hopefully nobody else."

1. As themeing improves and relevancy indicator determinance is sharpened can we expect to see drastic devaluing of off-topic or non-sensical links? Reciprocal or not?

2. What time period do you see this taking place over if at all and how suddenly do you imagine it would be implemented.

3. What technological shortfalls or even logistical shortfalls are keeping filters like this from existing in full force currently?