With the advent of online places to record family history, many people now keep all their family data on a website--and often on only one website. Those websites are fantastic places to add your family information and share it along with photos and documents and audio recordings with your extended family.
But, be careful not to have all of your information in only one place. There is great safety and peace of mind in redundancy.
For example, if you keep all your family history information on FamilySearch Family Tree, and only there, you could lose valuable information if someone comes in and makes an incorrect merge or significantly changes family relationships. In addition, you'll have no record of how you reached your conclusions, so getting things corrected could be very difficult.
I make a point of having my data in multiple places and formats. I keep information on FamilySearch Family Tree; I have trees on MyHeritage and Ancestry.com. I have a personal data manager on my computer and one on my iPad. And I have paper copies of everything in binders. I keep a file with all of my research notes, documenting my search efforts. I keep a paper copy and another copy in a file on my computer that I save in cloud storage.
More work? Yep, but not really as much as it seems at first blush. And once it's a habit to record things more than one place, it's just part of the research process. A lot of paper? Yes, but paper is still the most reliable way to store data. If I happen to tap the wrong spot on a piece of paper, the words don't all suddenly disappear. If my book case falls over, the data is still in my binders--maybe scattered about a little, but easier to find again than if my hard drive crashes.
Might be worth thinking about. How easy would it be to recreate your tree if you woke up tomorrow and Ancestry.com or FamilySearch.org didn't exist any more or someone had hacked your account and decided to have fun with your family data? Or if your house burned to the ground, would you be able to find all the stuff you now have on paper somewhere else? I put a lot of effort into finding the records of my ancestors. I want to be sure I can find the results of my efforts no matter what.