yes, this is actually a very easy way to get some Delta miles. Both myself and Mrs. PedroNY already did this recently. Make sure you chose "Medalion Member" when you register you will get 3,500 miles (I really do not believe their system double checks that) instead of 2,000 miles.
You will need to open up an idividual account, chose the cheapest (free) option. You will need to link a checking account (of any kind based in U.S.), that takes about 1-2 business days. Then you should transfer $5 from it to your Sharebuilder account. Then you should go and chose "automatic" plan under trading. You can buy $1 of any share listed on U.S. stockexchanges, the commission will be $4. You will want to chose "one-time" instead of reoccuring. You can chose the next closest Tuesday of when you want to make this transaction (Tuesday is the only day of the week allowed under this plan). After the Tuesday passes, you will be a proud owner of $1 in a share of your choice (with 400% commission charge, $4), and you will get Delta miles credited there after. The whole process from start to finish is about 2-3 weeks, miles post pretty quick.
You get 3,500 miles for $5, not too bad.
I hope this helps.
Best,
PedroNY