There are much smaller cameras without anti-alias filters. The Olympus PEN E-PL5 uses a 4/3 sensor and the Fuji X20 uses a 12 megapixels 2/3" sensor which is only slightly larger than sensors of compact cameras and even lower resolution.

What is seems like to me - and I am speculating - is that most digital cameras had anti-alias filters because everyone else was doing it. Then, when Nikon used it to give an edge to the D800E over the D800, other manufacturers followed suit in order to gain a comparable edge as well.

The truth is that an anti-alias filter was never absolutely needed. It compromises on image quality, trading fine details for a lower risk of moire. Yet, even cameras with anti-alias filter can still show moire because the filters may not be strong enough to avoid moire completely. You can see this in my comparison of the Pentax K-5 IIs and K-5 II. Play with the aperture controls in the demo towards the bottom of the page and you will see how both cameras exhibit moire.

While it would be possible to create an anti-alias filter to avoid moire completely, it would result in unacceptable softness, particularly when comparing with cameras having weaker anti-alias filters.

The next step in evolution is that some cameras will have built-in processing to reduce moire and that will encourage more cameras without anti-alias filters.