Some of the early products are this way. They changed almost everyday depending on who called you and none of the code had documentation or comments so you were left reading it. Some of the older code is still out there without comments but about a year ago we got everyone into the habit of doing comments if no documentation (self documenting). All and all things have gotten much better. It takes me about and 8th the time to figure out what to change to correct most situations and we forced the end users to go thru a project manager who would validate need, time and priority (which priority was the key, no more now stuff). But as David states it is a pain.

I agree with everyone here on comment header blocks with details of who, when and why in them. Maybe MS will move this into SQL like they have done with column and other comments so you don't have to do this but I doubt it.