Still seems to me some prospects will be disappointed....feel tricked...Can you afford to have that happen...even once?
You are going too extreme though, because in the fine print it will say "NO PURCHASE NECESSARY", just like when you are advertising CDs for 1.00% for one year and then in the fine print it says you need a minimum deposit of $1,000.00, some customers will feel tricked because they only have $500.00 to open.
There is a reason you have the fine print at the bottom providing necessary information. Also, let's not be naive, consumers today are trained to read the fine print. Also, it is not like you are misleading them, opening an account does enter you. When they read the fine print, the first thing they read is "NO PURCHASE NECESSARY:" with an explaination of how to enter.