Letter from Lex: high wire acts High wire acts are fascinating entertainment - until, that is, they end in tragedy. For most of this week, investors have taken the brinkmanship being played out in the US - which resulted in large tranches of the federal government being shut down - in their stride, although a ripple effect on financial markets was becoming more evident as the days wore on. Plainly, though, the potential for a default should Republicans and Democrats fail to reach a deal to raise the debt ceiling by October 17, hangs heavy. And what happens at federal level has a mirror effect at the level of the 50 states, with implications for municipal bond prices and yields. US politicians were not the only ones living dangerously, though. Across the pond, Italy's politicians indulged in a spate of brinkmanship of their own. Happily, this was resolved at a political level rather more quickly than the American shenanigans. But it was a reminder that, beyond the politicians" machinations, the country's economic woes persist. That has a knock-on effect for domestic companies, suffering from high leverage and increasingly unable to duck their refinancing issues. Current upheavals at groups ranging from Telecom Italia to Alitalia and Finmeccanica are all testament to these problems. A few executives were chancing their arms, too. Twitter announced that it was planning a $1bn initial public offering, likely to value the company at about $12bn, in spite of the fact that its losses widened to almost $70m in the first half of this year (a period in which it made a number of acquisitions). Meanwhile, Zeinal Bava, who has been running both Portugal Telecom and Brazil's largest integrated telco Oi since June, unveiled ambitious plans to merge the two groups. This would simplify their interlinked shareholding structures, and create a group with almost $17bn in annual sales. But Oi's investors may need persuading that coughing up for a R$8bn cash call as part of the deal is worthwhile given that the merged group will still carry substantial leverage. The possibility of falling off the tightrope, meanwhile, is the flip side to lofty performance. That has been the fate of several bank bosses recently, and at the weekend Intesa Sanpaolo's Enrico Cucchiani joined them, in spite of a reasonable, if unspectacular, tenure at the Italian bank. Investors in Siemens have also seen top-level changes recently, although the German behemoth's announcement this week that it was cutting 15,000 jobs worldwide had more to do with an existing restructuring strategy than any fresh plans from new boss Joe Kaeser. And at Sotheby's, hedge fund manager Dan Loeb is calling for chief executive William Ruprecht to step down - raising the question of whether a wealthy buyer might found to take the auction house private. Some executives, though, just bounce back. Mick Davis, founder and boss of Xstrata before its merger with Glencore, departed the public stage briefly earlier this year. Now he has returned with plans to build a new diversified global miner. It will be called X2.