Toyota does this for very good reasons. Here are a few:
1) These ports keep a constant vacuum inside of the crank case which help seals (such as cam and crankshaft seals) seal, and this vacuum helps maintain a large difference in cylinder-to-crank case pressures, which help the piston oil rings seal.
2) Intake valves. The light oil vapors that are introduced to the intake help lubricate the intake valves as they are seating, and also the valve stems.
3) The engine is not designed to have excessive oil exiting through these ports, only light vapors. If you see an engine with the small valve cover air filter vents that has oil puking all over it, then this engine likely has compression blow-by past the pistons and are causing a high pressure inside of the crank case.
I am sure there are other beneficial factors in having intake vacuum scavenge the crank case, but these are surely the more important ones.
Regarding smog, remember that burning oil has very little effect to the pollutants that are being measured. Our old '87 4Runner would kick out blue smoke for 5 mins after every time you started it up, and I remember one time while getting smogged, it smoked so bad that the smog tech had to walk out side the building to get fresh air. The 4Runner sailed through smog with all figures well below even the average values. I would think that the increased amount of oil in the combustion chamber would cause the spark to misfire and thusly the engine pollute, but this apparently is not the case. (?)
I have not seen a whole lot of newer engines, however of the ones I have seen still have plenty of intake lines sucking fumes from valve covers. They really are there for a reason.
I won't argue about gumming up everything. I've spent many hours cleaning out filthy intake manifolds, but again, this is a sign of other serious engine problems, such as worn out pistons and rings.
BigMike
Ahh mike well that makes a lot more sense to me. I left the rear line still connected so i still have vacuum running through the valve cover, i figured it would be good to leave at leased one in place. Im sure a lot of the gunk that was in mine was from the previous motor i had in because it didnt last too long.