Pushing this further, the question is portable *recommendations.*

From http://apml.org/geeks/usecases/ :

Example
uses might include…

Share and remix your APML
file across various services to create a rich profile of
your interests. Imagine having access to the interest
profile Amazon has created for you.
 
Convert your Lifestream RSS
feeds to APML to track your Attention across services (using
something like Engagd).

 
Upload your APML file to
Digg to get a customized view of Digg stories that match
your interests.
 
Use your APML to filter
incoming alerts (using something like
Particls)
 
Keep control of your own
Attention Profile – it’s very valuable (read
Your Rights).
  

Submit your APML to an
Attention Brokerage service to allow synchronized access to
your Attention Profile across all APML compatible services.
In this way all your sites and services can keep track of
your changing interests.