Not in Egypt, but I've recorded a couple large protests. Not only are they a great source of crowd sounds, but I feel that the recordings I've made are historically significant. The energy of those moments, and being in the middle of it with my gear, is also hard to forget.
In 2008, a couple days after the elections, I was watching TV in my LA apartment when all of a sudden I heard a loud ruckus outside. Being the sound nerd that I am, I grabbed my Sony PCM D1 and threw on my shoes. I quickly realized that it was a massive protest march against Proposition 8 (banning gay marriage in CA). Hundreds of people were marching down my street. I rolled record and joined the march. I ended up recording until the drive on my Sony filled up. Tons of chants demanding equal rights, horn honks, screaming, police siren wailers, police on megaphones yelling at the marchers blocking traffic, news helicopters etc..
I also recorded a May Day Immigrant Rights protest in Downtown Los Angeles once. Upwards of 5,000 migrant workers protesting for immigrant rights, drumming, yelling, megaphones, vuvuzelas. All bouncing off of the skyscrapers of Downtown LA. Wild stuff. You can hear a sample of those recordings here.
I've worked a few of these sounds into film projects, but I imagine in the end that they'll be more important historically. Hopefully, they'll make it in to a documentary someday down the road.