Just had a thought as to why it might not be universal... having it stored on their systems would probably mean additional requests to and from their servers for your Ignore list to compare. On your system though the active Ignoring could be handled entirely by your system. I mean it's not a heavy duty bit of processing, but if it was multiplied by every user on line and then piled on their servers?
Well maybe, but as someone that writes database driven websites, adding an ignore field to the database would be limited "processing power"....it would add to bandwidth more than anything....databases are designed to make thousands of connections at once....this forum is a database, and so is Facebook, Craigslist, IMDB, and several other sites