Hi fferen, I V iv V is indeed a super popular progression. You can see an example of it here: http://www.hooktheory.com/analysis/view/james-blunt/youre-be.... One cool thing about the way we store music (using relative notation) is that we can compare any two songs to see how similar they are harmonically. For example, there are several "similar songs" shown below the I V vi IV example in the link that all use the same progression in different keys.