Having MANY MANY empty columns in database

Hi All,

I want some clarification in the following,

In a database which we are having we have nearly 100 tables, and in 75% of
the tables we have 6 columns ( INT ) as standard columns. What is standard
columns, if you create a table in this database you should have some default
6 columns in there they should maintain
1. who is the owner of that read
2. when it is added
3. who is updating the record
4. when it is updated .... and other columns....

But many of the users are not doing anything with those columns, they are
all empty always....

Say in that 75 % of tables, 60 % table contains nearly 1000 records
always...

and other 10% of tables contains less than 10000 records

and 5% of table contain records nealy 5 lakh.....

What i need is???

If you drop those columns we will gain any performance or not.....
Definitely i know having that columns is not useful, but i want some
clarification that having empty columns will make performance degradation or
not....

Am using Debian, and having 1 GB RAM...
I want this informations in both postgres 7.4 and 8.1 ( don't ask me to use
8.3 please, i want info in 7.4 and 8.1 )...

Regards
SathiyaMoorthy