In my short time as a member of FT, I've observed that the more lucrative sign up bonuses are all targeted. (Personal and Business AMEX 75k , Chase Ink 80k, and the SPG 30k to name a few) In the past year or so since I've been on the look out for miles to collect I've only received 1 targeted offer for 50k with United.

I know there are ways around the targeted offers and that with the right CSR you can get them even if you're not targeted, but what's the secret to getting the offers directly? Are the reasons for being targeted all over the map? Or are there a couple of things one can do to receive more targeted offers?