September 10, 2013 3 min read

Opinions expressed by Entrepreneur contributors are their own.

Twitter is buying its way to a leading position as a platform for advertisers and media companies. Its acquisition of digital ad exchange MoPub, a marketplace where ad buyers and sellers can do business in real time, announced yesterday, is a major step in that direction.

On MoPub, buyers can place automated bids on ad inventory as soon as it is created, while sellers can manage and optimize their inventory. With a reported purchase price of $350 million in stock, MoPub is the most expensive startup Twitter has bought so far this year.

But it is far from the only one. As it has expanded into mobile, analytics and second-screen viewing, the seven-year-old social network has snapped up companies that can help it further its goals, from under-the-radar outfits such as Ubalo to larger companies such as Crashlytics, which reportedly sold for nine figures.

Related: Twitter's Jack Dorsey on How Entrepreneurs Should Use Twitter

Kevin Weil, Twitter's vice president of revenue product, said in a company blog post that Twitter wants to capitalize on the fact that it "sits at the intersection" of two leading trends in the world of advertising: the turn toward mobile, and the industry-wide shift to programmatic ad buying.

MoPub will continue to serve clients other than Twitter, according to Weil. But along with investing in and improving MoPub's existing business, Twitter also plans to use the startup's technology to bring real-time bidding to the Twitter Ads platform.

Below are some fast facts on Twitter's acquisitions so far this year.

Startup: MoPub

Sale price: Reportedly $350 million in stock

Acquisition date: September 2013

What it is: A mobile-focused digital ad exchange that allows ad buyers and sellers to make automated transactions in real time.

Startup: Trendrr

Sale price: Undisclosed

Acquisition date: August 2013

What it is: A social analytics company that tracks conversations around TV viewership and provides associated insights to media companies.

Related: Twitter and Facebook Up Their Social TV Game

Startup: Marakana

Sale price: Undisclosed

Acquisition date: August 2013

What it is: A developer of open-source training for software engineers.

Startup: Spindle

Sale price: Undisclosed

Acquisition date: June 2013

What it is: A tool that uses geolocation and data from social networks to provide users with suggestions for things to do in their local area.

Startup: Lucky Sort

Sale price: Undisclosed

Acquisition date: May 2013

What it is: A company tackling how to make large data sets easier to analyze, summarize and visualize.

Startup: Ubalo

Sale price: Undisclosed

Acquisition date: May 2013

What it is: Computing technology outfit working to increase efficiency in large computing environments.

Startup: We Are Hunted

Sale price: Undisclosed

Acquisition date: April 2013

What it is: A streaming music service with recommendation features.

Startup: Bluefin Labs

Sale price: Estimated $50 million to $100 million

Acquisition date: February 2013

What it is: A data analytics company that tracks social-media reaction to TV programs and provides that data to TV networks and advertisers.

Startup: Crashlytics

Sale price: Reportedly $100 million in cash and stock

Acquisition date: January 2013

What it is: A startup that helps developers track down and fix bugs in their apps.

