Should I Always Fully Qualify Column Names In SQL?

Question

Out of interest when working with SQL statements should I always use the fully qualifed column name (tablename.columnname) even if only working with one table e.g.

Answer 1

Even the most well defined systems are subject to change. A new field could quite easily be introduced to a table causing ambiguity in an existing query.

Fully qualifying them protects you from this scenario.