We noticed this especially with Call of Duty 4: Modern Warfare, as well as with Halo 3.
It's unclear if the outages were caused by gamers spending more time on their consoles during the holidays, the influx of new gamers, or some other software or hardware problems that caused the issues.
There hasn't been an official announcement from Microsoft, but the site The Bitbag claims to have received a reply from an unnamed Microsoft representative stating "...we will definitely be doing something for our Gold members that weren't able to get online over the last week."