Johannesburg - Media and internet firm Naspers [JSE:NPN] reported a 13% gain in full-year profit on Monday, at the low end of its own estimates, and cautioned that its acquisition streak may slow.Naspers, which has avoided the media industry's rapid decline by focusing on developing markets and e-commerce, said core headline earnings per share totalled 1 612 cents in the year to end-March, compared with 1 426 cents a year earlier.The company considers core headline EPS, which exclude certain one-time items, to be the best measure of its underlying profit.Naspers said earlier this month it expected to report a 10% to 20% increase in profit. On a fully diluted basis, earnings rose 12%, compared with the average estimate for 35% growth in a poll of 9 analysts by Thomson Reuters.Revenue totalled R33.09bn, compared with R28bn a year earlier.Naspers' breakneck growth has been helped by its 35% stake in Tencent Holdings, China's biggest Internet firm. It also owns 29% of Russian Internet firm Mail.ru and has indirect stakes in Facebook and Zygna, which produces the popular "FarmVille" and "Mafia Wars" games.However, investors may be worrying that the aggressive pace of growth could be starting to slow. There is also some concern about the company's valuation, given that the stock price has more than trebled in a little over five years.Shares of Naspers are down 5% so far this year, slightly underperforming a 4.4% drop in South Africa's benchmark blue chip Top 40 - (Tradeable) [JSE:J200] index.* Fin24 is a Naspers publication.