Sequences...

I had a asked this question earlier and did not get a response, so here
it is again.

When implementing an "autoincrementing" field in several tables, is
common practice to create sequence for each table, or is it OK to use
just one sequence? I know right off the bat that if there was a
requirement that there be no holes in the key for a particualr table
that one sequence over multiple tables (like in check register) would
not do, but if this requirment is not there, would having one sequnence
for all (provided your projected number of total records in all the
tables is less than 4 billion) tables be OK?

Thanks...james