Some additional comments –
Some argue it’s “personal” use but you’re getting paid to use the music.
Note if you download a song from iTunes you can use it in iMovie but not Final Cut Pro. Interesting part of that particular license.
And I’ve always felt posting such clips on the web compounds the problem. You’re no longer just handing it to the couple (and whoever they distribute it to). You’re posting on the web for the general public. You’re advertising that you will use copyrighted music and accept payment for it.
It’s a risk not worth taking. You can cross the street millions of times while the light’s red without issue. You only need to get hit by a car once to be killed.
I use Smart Sound. There’s other great libraries though.
I’ve always found brides understanding when I explain the copyright issue. Ironically I found the corporate jobs much more difficult where producers INSIST that a given scene be got to a pop tune or movie soundtrack.