Your friends may be the most effective pitchmen. In

the latest sign that technology firms are increasingly

deploying users’ data to boost ads, Google announced

that it was changing its terms of service to allow the

[5] company to combine users’ posts, reviews and profile

photos in advertisements. Here’s how it works: a user

searching Google for, say, a date-night restaurant might

see text ads promoting a local eatery — along with a

friend’s face and review on the firm’s social network,

[10] Google+. A whopping 87% of the search giant’s $50 billion

in annual revenue comes from advertising, and Google is

betting this information will make ads clickier.

    Rival Facebook has already found that pitching

products with a friend’s endorsement — a Like or positive

[15] post – makes for more powerful ads, which accounted

for most of the social network’s $5 billion in revenue last

year. Research firm eMarketer estimates that the

so-called social-ad business will be worth $9.5 billion in

U.S. sales this year. But it can be a risky business. In

[20] August, a judge approved Facebook’s settlement of a

class-action suit over employing users in ads, and the

company agreed to give them control over when they’re

recruited to promote a product. “They’re still walking a

tightrope,” explains consultant Jake Wengroff of firms

[25] trying such ads. The practice, he says, can alienate users

and open companies to privacy suits. Still, given the

potential profits in better ads, analysts say it might be a

risk worth taking. Here’s a look at what companies are

trying.

[30] TWITTER

Brands can pay to have users’ tweets amplified across

the site — with permission. Retweets essentially become

easy marketing.

GOOGLE

[35] Google’s new ads won’t show up only in search; they

could also one day appear across services such as

e-mail and maps. Users can opt out.

INSTAGRAM

Facebook’s photo-sharing site says it plans to launch

[40] ads in the next few months. It backtracked last year on

a policy that would have given advertisers access to users’

photos.

FACEBOOK

Users’ Likes and photos can appear in ads targeted to

[45] their friends. Users can opt out.