Ian Hall writes in:

Just ordered from Bodybuilding.com and got this follow-up and thought it was an interesting way of doing some post-order marketing and outreach to build community. Take a product and talk about it, direct people to more information, and recommend additional things they could use to see better results. Dunno if it’s terribly innovative but I thought it was neat, clean, to the point, and, at least in my case, communicated genuine interest and care.