The new solid state drives (SSD) are great, fast, low power, reliable, too bad they are so expensive. Experts have just begun to realize that they may cause unexpected security issues too.
SSDs use NAND flash memory to store charges in memory cells, while the more common hard disk drive (HDD) stores information by magnetizing regions on a spinning disk. The basic HDD technology memory cells can be written many times, but the NAND flash memory cells have "endurance" limits of 10,000 to 1,000,000 write/erase cycles, and if you write to the same flash memory cell more than the "endurance" limit number of times it will not reliably store your data. The SSD designers try to minimize the endurance limit problem by intentionally writing new data to less used locations. This allows the SSD to save new data many more times than the endurance limit.
The problem occurs when someone is used to using a HDD and they expect information deleted from the HDD will be overwritten with new data quite soon, but the SSD memory mapping algorithm deliberately maximizes the length of time that deleted data will be recoverable.
Remember that deleting proprietary information from your hard drive doesn't mean it's gone, until you actually overwrite the data someone else can probably recover your information, and the new solid state drives will exacerbate this problem by making it much harder to overwrite your deleted data.