Multiple SRF right after SELECT

Hi,

I wonder, if the following is correct and provides expected result:

test=# select generate_series(1, 2), generate_series(1, 4);
generate_series | generate_series
-----------------+-----------------
1 | 1
2 | 2
1 | 3
2 | 4
(4 rows)

Actually I have two questions on this:
1. Is it correct at all to use SRF in select list, w/o explicit FROM?
Why then we do not allow using subselects that return multiple rows?
I'd rather expect that these two things work in similar manner.
2. Why the query above provides 4 rows, not 2*4=8? Actually, that's
interesting -- I can use this query to find l.c.m. But it's defenetely
not that I'd expect before my try...
--
Best regards,
Nikolay