SAN FRANCISCO — Those long-forgotten posts on social networks, from the pasta someone photographed to the rant about her dentist, are forgotten no more. Social networks want to make them easier to find, and in some cases, to show them in ads.

Google on Friday announced that it would soon be able to show users’ names, photos, ratings and comments in ads across the Web, endorsing marketers’ products. Facebook already runs similar endorsement ads. But on Thursday it, too, took a step to show personal information more broadly by changing its search settings to make it harder for users to hide from other people trying to find them on the social network.

Both companies characterized these changes as minor updates. They are, though, the latest example of the continual push by Web companies to collate the reams of personal information shared online in the chase for profits. As Twitter prepares to go public and faces pressures to become profitable, it too will increasingly need to figure out how to make money from the information it collects.

Google and Facebook say that with the most recent changes, they are trying to offer users more comprehensive and personalized services. The problem, privacy advocates say, is when Web companies use or display the personal information of users in ways the authors did not expect when they originally posted it.