[manmal]

It's tempting to install such a system, but it would establish a strong tunnelblick for users. Also, what if I change my interests (interest reset button?)?

I could imagine an opt-out system, like "funding stories don't interest me at all", but then, Facebook's IPO would fall into that category and I followed it with interest.

[notyourwork]

I would assume you could tune or adjust your interests over time, similar to any other user specific preferences.

To your second point it is merely a matter or design choice. Does "funding stories as a whole" trump your more specific interest of Facebook IPO or does your specific interest in Facebook's IPO trump your desire to opt out of the funding stories as a whole.

The problem I see is making such a system intuitive to your user base and clear. It seems the more complex the system is the more complex the user preferences become.