Firstly - Im assuming that the couple wouldnt have a pro even if you werent doing it?
A lot of the posts here are really negative - sorry, but they are *ducks* Whatever
happened to encouragement!
My opinion stems from my own experience. My closest friend recently asked me to shoot her wedding (which I posted about on TP and got a lot of encouragement and support about). I was unsure, but decided to go for it. It was a really small wedding and she wouldnt have had a photographer if I hadnt done it. She knows I love my camera and am currently studying photography.
I dont have a fantastic kit, but I was damn sure I would do my best for her. I sat down with her and worked out a shot list, discussed timings for the day & booked us all into a local council owned stately home and private gardens for the shoot.
As said above, if you are unsure at all - talk it through with them and be certain you want the responsibility on your shoulders. If you dont - dont do it because you might not put your all into it!
My friends wedding had a very small wedding party - but this didnt stop it being stressful, I felt like a schoolteacher herding small kids about at some points - the wedding party were SO disobedient!! ;-) I eventually relaxed and enjoyed it.
And of course, the most important thing....they were delighted with their pictures.
Also..a few people mentioned they dont understand why people dont get a professional for their wedding - simple, money. I get married next year and cant afford a professional. And thats coming from someone who loves her photography. Believe me, I am absolutely devastated that we cant have a professional - but thats the way it has to be.