Kevin can elaborate, but we now infer a favorite tag based on what questions you visit, if we have a certain statistical confidence that you indeed love this tag. This is based on your history of what questions you've visited.
It's not actually stored in the database, though -- so if you set a favorite tag, it will override this behavior completely.
To elaborate...
We've started tracking the tags on the questions registered users visit. Our algorithm for selecting a "Frequented Tag" is: visited X questions with at least one tag seen Y times, and the most frequent tag is on at least Z% of those visited questions.
Currently, X=Y=Z=50
. Naturally I'll be tweaking these numbers as needed, but they seem to be working fine right now.
This data does decay over time, so you should never get "locked in" to a specific tag.
Also, as Jeff mentioned, setting an Interesting or Ignored tag on your user preferences page will suppress all of this.
UPDATE
To alleviate the "everything's orange" problem, if one of your interesting/frequented/ignored tags is in the list of tags on a /questions/tagged/{tags}
page highlighting for that tag will be disabled.
For instance, if your interesting tags are java
and android
, going to Questions Tagged java will cause only android
tagged questions to be highlighted.
This code will go out with our next build.
+
s in that tag have caused all sorts of problems in the past; it's possibly related to that