Very serious! Here's a few things to consider:
- companies can fire you at any moment without any prior notice if they find out that you have a conviction--if you did not include it on your application.
- the law actually allows companies to deny you a job based solely on the reason that you were arrested.
- your criminal record is available to anyone and by that we don't mean only your employer but also your co-workers.
- landlords and public housing authorities can deny you housing based solely on your criminal record.