No, it's not what you're thinking; this raid was a "Bear Raid". A "Bear Raid" is a stock trading scenario in which pundits attempt to artificially lower the price of a stock for their own profit.
It started last week when a couple of provocative articles appeared on Seeking Alpha, suggesting that 3D Systems' accounting practices were not exactly correct. On the surface this appears to be a legit analysis, and perhaps there are truths in there, but there's other things at play.
What's going on? It has to do with trading stock options, in which a trader owns an option to purchase or sell a stock at a future date. If a stock price drifts lower than the price are able to sell, they win. Conversely, if a stock price rises higher than the price they are able to purchase, they also win.
It turns out that this seems to be the case; a Bear Raid was underway. 3D Systems issued an official statement on this, saying:
We are aware of certain recent articles and their materially inaccurate and misleading conclusions. We reaffirm the accuracy of our public filings and accounting methods in all respects, and are pursuing legal remedies to hold those responsible parties accountable for what appears to be malicious, irresponsible and self-serving articles.
As with anything you read on the Internet, your mileage may vary, particularly with stock analyses.
Via Seeking Alpha (Hat tip to James)