I found this article quite interesting.
... the study confounded infectious-disease experts in suggesting that people vaccinated against seasonal flu are twice as likely to catch swine flu.
I get a flu shot every year. I haven't had a bad flu in a while. This summer I came down with H1N1 (confirmed by a nose swab).
I will say this: while I may have come down with it more easily, I have to say that for a flu infection, the symptoms I had were overall quite mild. The last time I had the flu I felt like I was going to die. This one gave me a 3-day fever, some coughing that never even kept me up at night, and weakness and a little light-headedness for a week or two after. Never messed with my sinuses.
I wonder if there's also a cause and effect for seasonal flu shots and the severity of H1N1 if you ultimately catch it. Because I'll trade "catch it more easily" for "wasn't all that bad in the grand scheme of things" any day, compared to the alternative.