Increasing numbers of very qualified and very accomplished American citizens are being forced to relocate abroad. Here's why:
I didn't move to the UK because I was a huge fan of the weather, or the food , or the transportation , or the dentistry. I moved here for immigration reasons.
When people ask me why in the world I left San Francisco to move to England, the typical answer I give is "family reasons." Which is true, but not incredibly descriptive. I think it's time to give a fuller story, and in the process out myself. 
When I moved here I was in a long term relationship with a British citizen. He had moved to the US with an L-1 Treaty Trader visa , and was hoping, nay praying, that this could be upgraded to an H1-B. Unfortunately, although he was an extremely experienced financial software pre-sales consultant, with a BS from a quite reasonable UK university, and paid quite significant taxes for precious little in return, this wasn't going to happen. We lived for several years under the threat that if his firm decided to let him go for whatever reason, he had two weeks to leave the country forever. Given that his firm wasn't doing particularly well at the time, this put a major strain on his life, and thus our relationship.
After New Labour was elected here in the UK, one of their first actions on taking power was to rationalize gay immigration rights. Essentially, they said that if you were in a same-sex domestic partnership akin to marriage, that would be considered as though you were married for immigration purposes. Thus, I was able to move to the United Kingdom based on our relationship ; the converse was not true. We didn't have the option to get married in the US or the UK, and even if California had same-sex marriage at the time, it didn't matter for immigration purposes. 
I've been in the US for a quarter of a century, have paid taxes when I was working, am married to an American and have never asked for a dime of public help. But the US - alone among developed nations - still persecutes non-Americans for having HIV and regards my civil marriage as null and void and my husband as a total stranger to me.
Britain doesn't persecute people with HIV and never has; moreover, Britain would allow my husband and I to relocate together to England at any point. I'm not sure people fully understand what it's like to build a life with someone and to do all you can to contribute to a society - and yet be vulnerable at any moment to having your family torn apart by the government. But it's a strain that eventually becomes crippling: you have no security, no stability, no guarantee that you have a future you can count on. And that affects an American citizen, my husband, as well.
Why has America become such a callous outlier on these matters? Why is the government forcing more and more able, qualified, productive and talented citizens into a diaspora to protect their families? And why, even after a big victory for Obama and a Democratic Congress, is there not the slightest chance of any progress for the foreseeable future?
Because it's about gays. And we are still, in the eyes of the federal government, sub-human.