I dug around the Facebook app (latest from App Store) it’s 239.3mb compressed and about 380mb uncompressed. Halide is an impressive 9.4mb compressed and 20.7mb uncompressed.
I still kind of feel this is a little apples and oranges comparison. The major social networking apps inherintely are very feature rich. I’d be suprised if Facebook could actually get the app under 80–100mb compressed given localisations and sorts without cutting a lot of features. It’s a tough game and obviously not a priority for them.