swap problems

[Joep L. Blom]

Hi,
I have a puzzling problem.
My system (AMD Phenom II 4-core with 4 Gb memory) uses gradually more 
swap space. OS: Ubuntu 10.04 (Lucid)
I have gkrellm running from the start and see the swap space increase 
from 0 Mb to now (>8 days on) 4639 Mb.
Moreover my free memory is also decreasing (must be logical?). when I 
start I have approx. 2Gb free and now it's barely 700 Mb.
Has anybody an idea how to see what programs are so sloppy written that 
they don't release memory when they exit, or, which processes refuse to 
disappear and why the swap space isn't released.
When I try swapoff it can't perform as it doesn't have enough memory 
which I think is logical as > 4 Gb cannot be stored in memory. But why 
doesn't swapoff simply remove all garbage, except the space used by 
running processes.
I know, the most simple solution is to restart but IMHO it is M$ 
practice to program sloppy but I expected Open Source programs to behave 
better.
Has anybody ideas?
Joep