According to the Information Commissioner's Office, the apparent surge in data breaches of late is not unusual - it's just that more people are admitting to them. However, it still highlights an area of worry. The good news is there are things you can do to make your data more secure.
Change your passwords regularly. If it's not a policy setting on your organisation's network, nag the IT manager. A mix of upper and lower case, numbers and symbols is best.
Switch off your PC when it's not in use, or at least lock it, using Windows key + L. At some companies, Microsoft included, employees must lock their PCs whenever they leave their desks. If you pass an unattended unlocked PC, you are entitled to send an email to the whole organisation from that PC, declaring the owner's non-compliance in a humorous way. A bit of humiliation among fellow professionals is apparently a powerful deterrent, at least at Microsoft.
Consider holding a data amnesty in your office - a day when people are invited to remove data from their hard drives, hand in CDs from their desk drawers and remove data attachments (spreadsheets of donors participating in an event, for example) from web-based email accounts. Data in web-based email services is out of your control.
Make sure you read the data security policy and procedures in your employment handbook. If you don't have any, nag HR. According to software company Websense, one in five UK workers says that he or she doesn't really understand their company's security policy.
Lastly, if you know any ethical hackers - 'white hats', as they're known in the trade - get them to find any vulnerabilities in your system. Better they do it than someone else.