But what if the marriage didn't work out? You can collect under your divorced spouse's Social Security record if you were married longer than ten years. Social Security does not need to contact your former spouse to do this. Keep a copy of your marriage certificate and divorce decree and you should be fine.
If you were widowed, you can collect widow's benefits. If your spouse dies, you can collect under his or hers Social Security record when you turn 60, rather than waiting until full retirement age. If you are found disabled, you can collect when you turn 50. Again, if you were divorced when your ex-spouse died, you need to have been married ten years, then you can collect widow's benefits as well.
Same sex marriage is less fun is when it comes to SSI or Supplemental Security Income cases. Because these cases are need based, you need to have very few assets to qualify financially. If you are married, Social Security counts your spouse's earnings as well. This was not a problem if you were domestic partners. (I didn't say it was all good news!) If your spouse is working, you have to show that you have less than $3000 in assets and anything your spouse earns has to keep you under that limit.
You also have other limits involved with SSI. For example, you're only allowed to have one car per household. You're not allowed to have any money set aside in retirement accounts or any other accounts beyond the $3000 limit.
Suppose you have too much money or someone wants to make a gift of money to you, you can always use a special needs trust to keep your assets under the $3000 amount for SSI. Make sure you use a special needs trust attorney to set up the trust and you can use the money for different things while still receiving your benefits.
If you're on SSI, by all means, get married! You've worked long and hard for that right and I won't ever tell you not to get married. Just do some financial planning first to make sure you don't lose your benefits.