Get a backup photographer for wedding photos (sometimes free!)
Selecting secondary wedding photographer
Wedding photos are a lucrative business. There are many people currently employed in other industries (such as engineering or medicine, for example), who have been interested in wedding photos for decades, have been practicing for years with high-end equipment and were looking for months to become wedding photographers in the future. Generally, these individuals are very good photographers but need to build up their portfolio before going pro. In order to gain more experience in wedding photos, they will often seek out weddings and serve as wedding photographers for free.
Keep amateur photographers as backup only
Since such photographers usually do not have much experience working with wedding photos specifically, you should only rely on them being the "second photographer" at your wedding. Check your contract with your primary professional photographer before you hire or invite a secondary photographer - some photographers insist on being the only photographers at the wedding. If your professional photographer has a clause in the agreement about being the only photographer, we at WeddingVenture.com recommend looking for another primary wedding photographer - in our experience, no really good photographers have such insecurities.
How to find a secondary wedding photographer
If you work at a large company, chances are there is a photographers alias or email group where you can find people just like that. Photography students are another great resource when it comes to free backup wedding photos. Ask the local university or post a gig on Craigslist & interview a few interested people.
Why you might want to have a secondary photographer
You might ask why on earth you would want to have another photographer at your wedding in the first place. The main reasons for that are:
Your main photographer cannot be in two places at once.
While your professional photographer is shooting pictures of the bride getting ready for the ceremony, the backup photographer can shoot pictures of the groom (and vice versa).
Your budget may not allow you to hire the main photographer for the entire day.
Professional photographers are very expensive (we at WeddingVenture.com met some that charge $2000-3000 per hour). Generally, you will definitely want to have an professional photographer for the ceremony, couple's candid shots (that generally take place right after the ceremony and before reception commences), and perhaps some reception wedding photos. However, if you hire an expensive photographer for 2-4 hours, that will not cover the entire wedding (what about those "doing your hair and make-up" or "waiting for the wedding limo to arrive" morning shots? What if your reception continues until midnight?).
Have a dedicated backup photographer
In summary, a backup photographer (and especially a free one) is a better option than simply asking your friends to take your wedding pictures. For one, the backup photographer will take better pictures than your friends. In addition, the backup photographer will not be distracted by drinks, wedding catering or your beautiful single bridesmaids :)
Again, before you get the backup photographer though, make sure your professional photographer is fine with that. Some photographers have a very explicit point in their contract stating that they will be the only professional photographer at the ceremony (and a photographer who is getting experience to go pro may be a borderline).