Personally, I tend to send something along the lines of:
I'd love to place an order and buy XYZ with you, but I noticed you only accept PayPal and Credit Card. I really don't want to support malicious businesses such as PayPal, Visa, MasterCard, or the banking industry, because (in my humble opinion) they're very user-unfriendly, monopolistic, and even have hidden political agendas (remember the blocking of Wikileaks etc).
Would you please consider accepting Bitcoin payments? If you're not familiar with Bitcoin yet, see www.bitcoin.org or www.weusecoins.com for a starting point and further details. Tons of information is available online. Bitcoin is great *especially* for online merchants such as yourselves. Most importantly, Bitcoin is "free" (as in free speech), secure, easy, fast, and best of all: not owned or controlled by any person or company or authority.
Note that even if you don't want to receive any actual bitcoins yourself, by using a payment provider (such as bitpay.com or coinbase.com etc) you can immediately accept bitcoin payments, and receive the money in euros or dollars. Extremely easy to setup, and still with much lower fees than paypal or credit card providers dare to charge. And ZERO risk of chargebacks, fraud, or other typical problems with online payments. Best of both worlds!
One more thing: if you start accepting Bitcoin, it would also generate lots of publicity amongst the Bitcoin community. Bitcoin users are typically enthusiastic, generous, and rapidly growing in number, so that would result in even more orders.
I would definitely like to spend money with you guys, but I will not support paypal or similar evil industries. As soon as you support Bitcoin, I'll place my order.
Thanks for your consideration!
Feedback, suggestions, or other "Bitcoin support requests": post them here!