There have been a lot of posts asking about the affect of CC apps on one's FICO score. Here is one case study, FWIW -- YMMV.

I have obtained 7 cards in the last 8 weeks:

HHonors AMEX Plat
PP Elite MC
Citi AAdvantage MC
Citi AAdvantage Business MC
Chase United Plus Visa
Chase United Plus Business Visa
Alaska Airlines Signature Visa

I checked my FICO before starting on this experiment and have tracked it since. It was 792. Seven cards and many miles and points and a boat load of credit later, my FICO is now 753 as of today.

For me, this is not a big deal. I am not buying a house or taking out a loan anytime soon. (Still, I will be in a cooling period for a while, as I would like to keep it above 750.) But for those who are looking to buy a house or something soon and who also want to collect cards for miles, I would recommend some restraint and perhaps some vigilence in tracking the FICO. According to published reports, above 750 gets 5.98% while below 750 gets 6.2%. I don't know the veracity of these figures; I am just reporting what the FICO tracking folks will tell you. I understand that lenders may also use other factors (such as income) in judging the rate they will offer. In any event, given that 7 cards resulted in a swing of 40 points, I suspect that a card or two here or there would not result in such a large swing.

Hope this helps. Good luck!

-N