When NOT to index small tables?

I have found many reasons not to index small tables (see .
But I still have questions.

1. How small is small enough?
2. am I supposed to drop primary key index on so called 'label tables'
knowing I am using this pk in join clause?
3. Is it good to drop index on small table If I know I have created VIEW and
joined large table and the small one
and I have where condition on that particular colum?
Ilustrative example:
table small
{
id -- primary key
colum_for_where_condition -- index or not to index?
}
table large
{
...
fk_for_small_table -- indexed
...
}
create view as select .....
inner join on common_column ..
I have migrated from mysql .
I have found that complex view expression takes about 10 sec using ordinary
planner,
but genetic alg takes about 5 sec. Strange?
I can give details if someone is interested.

Regards,
Alvis