added, 12/06/02, RAR
The following paragraphs are quoted the from a 1994 Scientific American paper . Comments are added in italics following each paragraph from the paper.
The Self-Reproducing Inflationary Universe
Recent versions of the inflationary scenario describe the universe as a self-generating fractal that sprouts other inflationary universes
(i. e., this is a multi-universe model)
by Andrei Linde, Stanford University
"Although the COBE results agree with the predictions of inflation, it would be premature to claim that COBE has confirmed the inflationary theory. But it is certainly true that the results obtained by the satellite at their current level of precision could have definitively disproved most inflationary models, and it did not happen. At present, no other theory can simultaneously explain why the universe is so homogeneous and still predict the ripples in space discovered by COBE."
Of course, this definition of homogeneous ignores all of the periodic galaxy spacing data, and assumes that the "ripples" in the Cosmic Microwave Background are the, as yet unproven, cause of galaxy formation, etc., instead of just being experimental noise.
"Nevertheless, we should keep an open mind. The possibility exists that some new observational data may contradict inflationary cosmology. For example, if observations tell us that the density of the universe is considerably different from the critical density, which corresponds to a flat universe, inflationary cosmology will face a real challenge. (It may be possible to resolve this problem if it appears, but it is fairly complex.)"
Again, dark matter or dark energy are needed to make up the missing mass, since the observed mass is much too low to provide a critical density as defined by General Relativity (again, assuming that General Relativity governs the motion of the universe).
"Another complication has a purely theoretical origin. Inflationary models are based on the theory of elementary particles, and this theory by itself is not completely established."
As commented in the section on Quantum theory, not all of the "known" elementary exchange particles in the Standard Model (such as the strong-force gluons, that are assumed to be very massive) have been observed. The photon exchange mechanism for electromagnetic force is dubious for widely spaced charges, and the gravitational force exchange mechanism using gravitons is totally unknown. Only the exchange bosons (W+ ,W- and Z0) for the weak force have been experimentally measured, and no one has explained why such massive particles are needed to stimulate decay reactions having Q values of a few MeV (in particular, for the decay of a free neutron into a proton, the exchange boson is about 100 times as massive as either particle)! Researchers at Brookhaven National Laboratory now have experimental evidence that quarks account for only about 20% of the spin of a proton, so they are looking for the origin of the rest of the spin (could it be related to the rotation of the quark and diquark around each other?). Another recently discovered phenomenon is the "toggling" back and forth of neutrinos from electron to muon to tau on their way from the Sun, which seems to explain the "neutrino deficit" but then casts doubt on the validity of the Standard Model of particle physics!
 Andrei Linde, "The Self-Reproducing Inflationary Universe", Scientific American, Vol. 271, No. 5, pages 48-55, November 1994.
 "Researchers seek answers to proton spin mystery", Nuclear News, Vol. 45, No. 2, pages 68-69, February 2002.