I know they are a nuisance (esp when you hit them) but they do serve a purpose. I though some statistics may highlight the reason for them - these are the number of posts per month since the forum started
2000 Mar 156
2000 Apr 293
2000 May 782
2000 Jun 1,931
2000 Jul 1,198
2000 Aug 1,279
2000 Sep 487
2000 Oct 892
2000 Nov 662
2000 Dec 1,727
2001 Jan 3,470
2001 Feb 4,937
2001 Mar 7,524
2001 Apr 11,249
2001 May 13,362
2001 Jun 17,813
2001 Jul 18,979
2001 Aug 22,283
2001 Sep 20,675
2001 Oct 25,043
2001 Nov 23,940
2001 Dec 24,598
2002 Jan 29,458
2002 Feb 26,320
2002 Mar 13,837 (so far)
Without the limits the topics would scroll down so quickly that it would be hard to keep up and they would possibly not get the attention that they deserve.