10 of Wall Street's Big Losers This Week

It's been a volatile week for investors, but some stocks suffered far more than others this week. Let's take a look at some of this week's biggest losers -- where they were before the opening bell rang on Monday and what they cost just before Friday's closing bell.

The details behind the dive
BG Medicine issued a pair of generally upbeat press releases related to its heart failure diagnostics specialty, but investors apparently didn't hear what they wanted to out of the life sciences upstart.

Velti is a Dublin-based provider of mobile marketing services. Hailing from Ireland, given the country's dicey financial state, isn't very comforting, and neither is a business niche where Motricity (MOTR) saw its stock get pummeled last month. Velti completed a secondary offering at $15.25 a share less than three months ago, and now it's trading for a little more than half of that.

CardioNet shareholders skipped a beat after the Department of Justice began looking into allegations that the maker of wireless heart monitoring devices was overbilling Medicare. Investors don't like uncertainty, and neither do analysts. Roth Capital lowered its price target on CardioNet from $7.50 to $4.

It was terrible timing on Vanguard's part to go public earlier this summer at $18 a share. Hospital operators have taken a beating in light of spending cutbacks. There was no new material news out of Vanguard Health this week, though it did post its quarterly results late last week.

AuRico Gold agreed to buy Northgate Minerals (NXG) in a $1.5 billion deal. A miner marrying a miner may be perfectly acceptable in some states, but investors weren't too happy to see AuRico -- formerly known as Gammon Gold -- paying a 45% premium for Northgate.

AuRico wasn't the only stock to take a hit on the Northgate acquisition. Primero Mining had a deal in place to be acquired by Northgate, but now that deal is being terminated. Primero will be on the receiving end of a $25 million break-up fee, but that's not much of a consolation now that it will no longer be taken out itself at a market premium.

The only news out of Donegal Group this week is that its CEO and CFO will be participating in the Keefe, Bruyette & Woods 2011 Insurance Conference. This is usually a positive development for shareholders, since it gives the insurer a bigger stage to promote itself as an investment. However, like most thinly-traded stocks, things will be volatile from week to week.

Dex One received a compliance letter from the New York Stock Exchange last Friday, warning the marketing solutions provider that it has been trading below the exchange's minimum market cap requirement for more than 30 consecutive trading days. Dex One still has time to appeal the possible delisting.

Esterline fell sharply this morning after posting uninspiring quarterly results last night. It's not the slight dip in profitability that's scaring the market. Analysts were already counting on that happening. Esterline's iffy outlook -- warning about softness early in the next fiscal year and continuing military budget tightening -- did the trick.

H&R Block was sitting pretty through the first four days of the trading week. The tax prep giant saw its shares climb every single day through Thursday, amassing a weekly return of nearly 9% at the point. Those gains quickly evaporated after H&R Block posted a wider loss than expected for its latest quarter. The crummy quarter doesn't surprise me, and it shouldn't surprise you either.

Longtime Motley Fool contributor Rick Munarriz does not own shares in any of the stocks in this article, except for Motricity.