I always hated small dogs; thought they were yippy and hyper. We got a chihuahua for our daughter 6 years ago when she was 17. By the time she left home, we loved the dog too much to let her take her. We got another one last year and she's just the cutest little thing.
They are like babies that never grow up. Extremely portable; we take ours everywhere we travel. They are very protective. We have to watch the older one very carefully when strangers come around. They get along well with their own breed but don't like other dogs much. The exception being, we had a 5-year-old border collie mix when we got our first one. Being a puppy, she was fine with him and he's always been very tolerant and protective towards her.
In short, an excellent companion for older people.
http://i15.servimg.com/u/f15/11/05/90/13/xmasdr10.jpg
Sorry, couldn't figure out how to post a pic here. Hopefully the link works.