MarketWatch: Twitter may be ousting CEO Dick Costolo as part of a plan to jump-start growth, but the negative analyst commentary is piling up, and more are weighing in on the benefits of a takeover by Google. MKM Partners has downgraded the microblogging site to neutral from buy on concerns about stalling user growth and uncertainties surrounding its CEO search. “We see no catalyst for improving sentiment in the next two quarters (besides a possible Google bid),” Sanderson said in a note to clients. Google is the “natural acquirer if there is one” for Twitter because it has the cash, is facing increased advertising competition from Facebook and is struggling to compete in social media.