This is a very personal choice. Some women want to "get their money's worth". Some women have been well-advised that if they don't go large enough the first time, they could end up disappointed with the results a few months post-op. Some women simply relish the idea of having larger-than-average breasts, downplaying any negatives and embracing the positives.

Related links: 

• Dr Tom Pousti talks about large breast implants
• DocShop.com comments on large breast implants
• General comments on large breast implants
• Prepping for breast implant surgery, including a brief consideration of larger implants
• Obligatory Wikipedia reference