My MIL was a bit irresponsible, but it can't compare with some of the stories portrayed here.
The first time I ever met MIL she was in the hospital recovering from surgery. DBF (now DH) took me with him when he went to visit. We had a nice chat (although a bit difficult to understand since she didn't have her dentures in - later found out she only wore them to work), and then she needed to take her evening walk up and down the halls. As we were walking, she did inform me that I probably shouldn't walk behind her since she had been a bit gassy.

At least she gave me fair warning.
When we were planning wedding, MIL offered to either pay for the rehearsal dinner (with a very specific budget), or give us the cash if we wanted to cater it ourselves. Since my DH was a chef at the time, we decided to take the cash. We knew we could do it for less and use the money to help defray some other expenses. We never got a dime of the money, but she got new furniture and golf clubs.
She had a habit of discussing people she and DH knew years ago when he was a kid. She did seem to revel in making sure the discussion was a subject to which I had to knowledge and couldn't participate.
She called repeatedly to borrow $ from us for meds, etc. She also called one day from the medical equipment house. She wanted to borrow $1500 to buy GMIL an electric wheelchair. Of course DH tells her he needs to discuss it with me. Therefore, when WE decide not to do it because GMIL never leaves the house, it looks like I am the bad guy.
She lived in the same town we do and never once came to see her grandkids in 7 years. I finally made my DH start taking the kids to see her and GMIL while I went to WW meetings. So kids did get to know them a little bit before they died.
I don't believe she was a bad or evil woman, just completely oblivious. Luckily my DH has an awesome relationship with my DM. Last night we were discussing an Alaskan cruise for summer of '07. His comment was I hope your mom goes with us. I am so lucky that such a wonderful, responsible man came from such an irresponsible home.