The fourth week of July has been exciting for the blockchain and cryptocurrency world. Perhaps the biggest news is that controversial Tron (TRX) chief executive Justin Sun gave a public apology on social media for his recent conduct to hype a cryptocurrency industry event. Sun wrote a letter in Mandarin on Weibo Thursday, saying he sincerely apologizes to the public, media, officials, and regulatory authorities for over-marketing and publicizing a highly-anticipated charity lunch with billionaire investor Warren Buffett of Berkshire Hathaway (NYSE: BRK.A) fame. Sun did not specify which Chinese regulators he is referring. The letter came days after he postponed the lunch with Buffett, citing a health issue with kidney stones. It is unclear when the charity lunch between Sun and Buffett will be rescheduled.

Here is the rest of the week in review:

The US Internal Revenue Service (IRS) announced Friday that it is sending warning letters to taxpayers who own cryptocurrency, advising them to pay back taxes they may owe or to file amended income tax returns. In a news bulletin, the agency said that it began mailing what it called "educational letters" last week. The IRS disclosed that it sent letters to more than 10,000 taxpayers whose names were obtained from compliance efforts. IRS Commissioner Charles Rettig said that taxpayers should take these letters very serious...