Factbox: When M&A deals slam into regulatory roadblocks

NEW YORK (Reuters) -The Obama administration on Wednesday sued to block AT&T Inc's $39 billion acquisition of T-Mobile, launching its biggest challenge yet to a takeover and dealing the carrier a potentially costly blow.

Here are a few examples of major deals that have grappled with regulatory hurdles over the past few years:

DIRECTV-DISH

In 2001, the two leading U.S. satellite TV providers entered into a $26 billion agreement under which EchoStar, owner of Dish Network, would buy Hughes Electronics' DirecTV.

The U.S. Department of Justice and Federal Communications Commission strongly opposed the deal on antitrust grounds. Then-FCC Chair Michael Powell said the commission could not confirm the deal was in the public interest, adding that the cost to consumers was "staggering".

The deal would almost certainly have created an even more formidable rival to an entrenched cable industry. About a decade later, Powell joined cable industry group NCTA as its top executive.

Facing such stiff opposition, the two satellite companies withdrew their agreement in December 2002. As part of the merger agreement, EchoStar was required to pay Hughes a break-up fee of $600 million.

NBC-COMCAST

Comcast Corp managed to take control of NBC Universal in a $30 billion deal despite numerous objections from a broad swathe of interests, including minority groups and business rivals. Comcast bent over backwards to convince regulators that -- despite being the largest pay-TV and Internet access provider -- it would not glean an unfair advantage by owning one of the big four broadcasters.

Comcast announced the deal on December 2009 and closed it after regulatory approval in February of 2011.

TICKETMASTER-LIVE NATION

Live Nation's merger with TicketMaster Entertainment was small by U.S. business standards but hugely controversial from the minute it was announced.

The combination of the world's largest concert promoter with the No. 1 ticketing company unnerved everyone from fans and record labels to artists and their managers. It probably didn't help that Ticketmaster also owned the No. 1 artist management company -- Front Line.

The first major merger of the Obama administration era, announced in February 2009, took a year to gain approval. In the end, it was cleared with some restrictions but nothing that hurt the business, analysts say.

SIRIUS XM RADIO MERGER

The merger of Sirius Satellite Radio and XM Satellite Radio was one of the longest, most drawn-out merger processes of recent history. Regulators worried over the creation of a lone satellite radio company.

First, Sirius Satellite Radio's $4.59 billion purchase of rival XM Satellite Radio was given antitrust clearance by the Justice Department, which concluded that consumers could turn to many alternatives, including mobile phones and personal audio players.

But the traditional radio industry, consumer groups and some U.S. lawmakers criticized the deal, which brought entertainers such as talk show host Oprah Winfrey and shock-jock Howard Stern under one roof. In July 2008, the FCC let the deal proceed as long as the companies agreed to conditions to protect consumers and settle FCC enforcement matters, bringing Sirius XM's regulatory marathon to an end.

NASDAQ-ICE/NYSE EURONEXT

Nasdaq OMX Group Inc and IntercontinentalExchange withdrew a hostile $11.3 billion bid for rival NYSE Euronext in May 2011, citing opposition from U.S. antitrust regulators.

At the time, the U.S. Justice Department said that if the Nasdaq-ICE bid had not been abandoned, it would have filed a lawsuit to stop it. Combining Nasdaq and the NYSE would have brought together the top two U.S. stock exchanges, creating a virtual monopoly on listings and dominance in trading U.S. cash equities and options.

CVS CAREMARK

The March 2007 marriage of the largest retail pharmacy CVS and the second-largest pharmacy benefits manager Caremark Rx Inc raised eyebrows when it was announced. Consumer groups were concerned that the deal would hurt competition but ultimately CVS' $24 billion bid for Caremark received speedy antitrust approval.

CVS had to sweeten its bid for Caremark after a rival offer by Express Scripts Inc. But in 2009, eight lawmakers asked U.S. antitrust regulators to take the unusual step of reopening their investigation into the merger. The U.S. Federal Trade Commission started an investigation of the company's business practices that year, as several groups claimed the merger has led to higher prices, compromised quality of care and pushed patients to choose CVS drugstores over other pharmacies.

The investigation is ongoing.

(Reporting by Yinka Adegoke and Liana B. Baker; editing by Bernard Orr)