I'm not sure of the exact arrangement you are talking about but it seems to me unless the bearings each carry 100 lbs this will not work. Stacked one on top of another will not distribute the load to all four seperately but each will be carrying the full 400lbs. I may be missing something in your description.

Intrinsically, I have to say no. As suggested by blmcghee, the load will not be evenly distributed. If I assume you have a shaft with a shoulder, the bearing against the shoulder will carry the entire 400 lbs. I suppose you could shim each bearing to distribute the load, but fitting a 400 lb. single bearing has to be the easier way to go.

Blacksmith.

Interesting premise.
If one bearing had 4 stacked raceways which might
be a nightmare manufacturing wise, there would be
load sharing assuming there was no moment load to
consider.  In the case of 2 raceways in the same
bearing, the dynamic load carring capacity is generally
agreed to be 1.8 instead of 2.0, so I would assume
there would be continuous downgrading of the static load
carrying capacity.
If the bearings were just stacked, the top would see the 400
pounds and the second would see 400 pounds plus the weight
of the bearing above it, etc.

Consider angular contact ball bearings.

Rich

try this tech paper for some thoughts.
http://evolution.skf.com/gb/eng-article.asp?pkID=28

Yes it is able to be done but you hve to order special bearings that usualy do not interchange with standard bearing configurations. You should talk to the applications engineer at your bearing house (eg SKF, NTN, KOYO,TIMKEN, FAG etc) they will be able to look at what you are trying to achieve and then make a recomendation as to the best solution that they can offer. It is worth talking to several bearing manufactures as many special bearings are made by only one or two manufactures

no

Rich was correct.
angular contact bearings will share the load
assuming all of the raceways are contained within
the same outer and inner rings or for strictly
thrust bearings you would need concentric raceways
in the upper and lower rings.  Radial bearing are
used this way, but I have just begin to see applications
for windmills where they are using two row angular
contact bearings to share radial, thrust, and moment
loads.  

This would require deflection in the system for the four bearings to support the load. Even so you would not likely find them loaded equally, and the limits would be established by the stiffness of the support structure/mountings, not the strength of the bearings.

Crash 'holding up my end' Johnson

Snowcrash is right BUT (and this is where the dialogue probably becomes meaningless with respect to the original query)the inequality of the load sharing would become minimal if the manufacturing tolerances of the shaft, housing, raceways etc were fine enough.  This may sound like nonsense but consider the Moore Tool double Vee guideways; the only reason these work is the care that is taken a) grading the rollers and b) hand lapping the Vees.  The nature of a Hertzian contact is that most of the deformation will take place at a relatively low percentage of the load.

Rich