There are some interesting comments on the site, one from a woman who was internationally adopted and never told about it. Her adoptive parents died in a car crash without telling her who she was and she only found out when:
One day USCIS did a routine record search and found they lost my adoption decree out of my file. They came to me for a copy, which is when I found out I was adopted--because I couldn't produce the adoption paper, they declared me undocumented and civilly detained me for three years, first in prison, then in a Texas deportation camp, until I located the courthouse where my adoption paper was filed and gave ICE a copy.
Because my parents weren't honest with me, it screwed up my life. I had a scholarship to go to art college at the time ICE detained me--by the time I got out three years later, that scholarship was gone. I wanted to be a police or FBI sketch artist--that was gone too because I spent time in ICE detention as an undocumented and therefore ineligible for any government job. I'm married now, have two kids, my youngest son is autistic--and Social Services just denied his re-certification for medical assistance (in our municipality, I have to apply for medical assistance for him so he can get educational assistance for school) because Homeland Security's eVerify system screwed up (I have a naturalization certificate issued when I left the deportation camp but the system said I didn't. I had to take a day off work and go to immigration to fix it.)
Search for the truth, if you feel you must... But love your family for being your family. They are still there for you and always will be, I'm sure.
Dad was a Korean and Vietnam vet and Mom was a Korean War Bride he brought back after he Korean War. I had a happy childhood. I was spoiled rotten. I got whatever I wanted--music lessons, drawing lessons, dance lessons, all the books I wanted to read. I went to private school wherever we moved, the best education, the best everything. Except the truth--and because I didn't have the truth, it screwed up the rest of my life. so while I love my parents and had a happy childhood I struggled with anger for the first year I was in prison because if they'd told me the truth none of this would have ever happened. I still have mixed emotions about the whole thing, and a lot of questions I will never have answers for.
Most people won't go through anything like this, but it does seem important to know where you come from for a number of reasons - identity, medical history, possible relations, etc. My 3 year old son already knows he's adopted (it's kind of obvious as he's Chinese, but we told him very early so he could understand the adoption process and the constant comments we got from other people and learn to deal with them). We also tracked down and visited the person who found him through the police records, interviewed his carers in the orphanage and saved the newspaper pictures announcing where and when he had been found, so we have as full a history as possible (back to about week 1). We don't want to make the first part of his life a bigger deal than it needs to be, but we figured that we should make the information available to him if he wants to explore his roots.
One of the interesting things we discovered when visiting the person who discovered him was that it's quite possible she knows more than she's telling us. Many Chinese women who 'abandon' their children do so because they feel they don't have a choice, and very few make the decision themselves. There's a high fine if they are caught abandoning a child or giving a child up to the orphanage, but they often send someone to check on the baby in the orphanage, who will also often report back on any adoption. While the orphanage always places an advert in the local paper seeking the birth parents before allowing any child to be adopted, they almost never come forward due to the fine for abandoning the baby. In our case, we found out that the woman who found our son was a student in another province with no family or friends in our city. She decided to take the 12 hour train journey to our city (for a half-day visit) and just happened to be walking around a small park when she saw a baby. She told us that she felt guilty for not taking the baby home (why?), but decided to report it to the police instead as she felt her studies would be affected if she was also looking after a child. I doubt she's the actual mother (he couldn't have been more than about a week old at the time, so she would still have looked pregnant), but she may know who the mother is. We didn't ask any awkward questions, but we still keep in contact and may find out more in the future.
Edit: sorry about the wall of text.