Edit - 3.5 months not 2.5, had to look it up to make sure I wasn't bullshitting myself.
Well for anyone not into fitness: This is what are known as "newbie gains" i.e. the amazing gains everyone makes when they first start out.
These are generally a mix of strength gain, improving technique, motivation and improving pain tolerance ( and sometimes weight loss).
Your wife won't be able to triple her current deadlift again in 2 months, for instance, since now that she's started, every gain becomes smaller and smaller.
This is important because the 100 pushup program doesn't promise that you'll just improve or go from doing 1 pushup to 10, they claim you can do 100 consecutive ones on week 7.
My "tripling your strength" number just came from what I know to be about the average number of good form pushups most fit people I know can manage. These people are thin, fit and train relatively often, which means they are no longer fitness newcomers.
For instance, I look like this and can do maybe 20-30:
http://www.thepoxbox.com/contentimages2/workoutdone4.jpgSo while most people will embark on this "100 pushup" plan and make AMAZING improvements at first, they will quickly plateau as their technique and motivation ( and probably cheating) reaches their body's true current potential and then the amazing streak of gains will stop and they are liable to just quit, having learned nothing about fitness and just returning to bad habits and not understanding why they failed to reach a goal that was impossible in the first place...