U.S. stocks finished lower on Thursday, for a third-straight day of losses, as the benchmark S&P 500, and the narrower Dow Jones Industrial Average, (^DJI 0.56%) both declined 0.7%. The technology-heavy Nasdaq Composite Index (^IXIC -2.05%) lost just 0.8%.

From short-term performance to long-term forecasts (the only ones worth paying any attention to): This afternoon, asset manager GMO released its seven-year asset class return forecasts as of the end of last month. The numbers make for grim reading.

GMO's forecasts -- which have had a good predictive track record -- have large-capitalization U.S. stocks returning an annualized loss of 1.5% after inflation, while small-cap U.S. stocks are expected to do substantially worse, with an annualized loss of 4.5%. The final U.S. stock category for which GMO publishes a projection, "High Quality" is at least supposed to produce an annualized gain, albeit a rather slim one, at +2.3%. The conclusion: Stay committed to a very long investing time horizon (i.e. longer than seven years), and keep saving regularly. Alternatively, if you have the expertise, time, and inclination to pick stocks -- and most individual investors don't -- plying that craft could make a significant difference to your returns.

Twitter: Still finding itself

Source: Twitter

In a statement filed with the SEC today, Twitter (TWTR) announced the resignation -- effective immediately -- of chief operating officer Ali Rowghani, the third high-profile executive to leave the micro-blogging company this year. Twitter chief engineer Chris Fry left at the end of May, and Michael Sippey, vice-president of consumer product, left in January.

Mr. Rowghani was tasked with a key objective: Widening Twitter's appeal in order to reach a mainstream audience and become a genuine competitor for Facebook (META -4.13%), which, incidentally just scored a high-profile hire this week, luring Paypal president David Marcus away from eBay in order to head up Facebook's mobile messaging unit. Twitter has 255 million monthly active users, only a fifth of Facebook's total.

Following a huge post-IPO run-up in its share price, Twitter's first two sets of quarterly results have raised serious doubts about its ability to achieve that goal, with the user count growing just 6% sequentially last quarter. Rightly so, in my opinion -- I simply don't believe Twitter's format and structure is consistent with broad appeal.

People know why they join Facebook -- to connect with their friends and family. However, outside certain professions -- journalism, for example -- Twitter is having a hard time convincing people that it's a must have; in fact, it's struggling just to provide a clear pitch of what the service is, to begin with. Twitter shares are down 42% year to date.

Mr. Rowghani had been pushing for Twitter to acquire online music sharing site SoundCloud or consider buying another streaming music platform, which seems a bit harebrained, and doesn't address the company's aforementioned core challenge, which is that it doesn't know what it is or what it wants to be. Twitter will not replace Mr. Rowghani; instead, CEO Dick Costolo will now be responsible for the development/redesign of the site; at least no one will be able to say that the issue isn't getting attention from top management. Still, I think this is evidence that Twitter went public too early. Furthermore, with the stock still trading at nearly 14 times sales, there is reason to believe the correction could have further to run.