Paid clicks at Google have rebounded nicely since the beginning of this year, according to recent numbers from comScore. But a new report from one research firm has a serious warning for the online advertising industry.

According to The Stanford Group, initiatives by state legislatures in New York and Connecticut to beef up online privacy laws could undermine growth in the digital advertising business. The FTC has also begun to look into questions of online privacy  

"We think the growing government scrutiny is likely to make it easier for consumers to opt-out of behavioral tracking, which in turn will reduce the number of web surfers that can be reached through behavioral advertising," The Stanford Group said in a statement.

That could be bad news for companies like Google, Yahoo and Microsoft, which have positioned themselves atop a massive heap of user data.

As for Google's present situation, the search giant reportedly saw a 19.6 percent spike in its paid clicks business for the month of April compared to the same time last year.

Google, which earlier this year modified the way it counts clicks, took a beating from comScore and Wall Street throughout February and March on fears that its paid clicks business was suffering from a larger economic slowdown. But by April, Google had rebounded, and the current comScore report suggests continued vitality at the company. However, Lehman Brothers analyst Douglas Anmuth said he was somewhat cautious about the data because it only counted Google's U.S. clicks.   

Meanwhile, both Microsoft and Yahoo saw their paid clicks drop. Yahoo fell by 4.4 percent, compared to 9 percent for Microsoft, which has taken to offering cash incentives to people who use the company's search engine.