If we're going to compare sizes, then we should compare properly.
Pentax *ist DL2 (DSLR), Pentax MX (SLR, probably the smallest 35mm SLR ever made), Panasonic GF1. Lenses are 18-55mm on the *ist, 50mm on the MX, and 14-45mm on the GF1.
Front:
The DSLR is way bigger than both the classic MX and the GF1.
This is obvious when you look at it from an oblique angle, the bulk of the DSLR is plain to see.
Top:
You can see how thick the DSLR is, even if you took away the bulge at the front.
The body of the MX and the GF1 are a similar thickness, but if you include the protruding mirror box/K mount, it is quite a bit thicker, because of the flange/registration distance, 45.5mm vs 20mm).
Notice how the MX and the GF1 are a similar size overall, but the MX has a prime lens while the GF1 has a zoom. If we compare like with like, then we need to show both cameras with a similar zoom range.
GF1 with 14-45mm (28-90mm equiv)
MX with 18-55mm (27-82mm equiv)
It's obvious now, that if Pentax could make an EVIL camera the size of the MX, but with a Pentax K mount, it would be a lot larger than the overall package that micro 4/3 delivers. Pentax COULD make a smaller zoom, but as Sony has shown, you can't get an 18-55mm lens too much smaller and still expect reasonable quality on an APS-C sensor.