Public Cloud has some advantages – generally a low upfront cost with practically infinite scalability. But it has its disadvantages:
Service Levels – providers often have no SLAs at all so uptime, performance, service quality etc., fluctuate with user demand.
Network Dependence – performance is limited by the Internet, which may slow down at peak times, reducing or halting employee productivity.
Privacy Compliance – it is next to impossible to be compliant with HIPAA, privacy, PCI Data Security Standard, Federal Rules of Civil Procedure, and audit requirements.
Vulnerability – there are no guarantees for timely patching, malware protection, security of confidential data, in-house administrator access restrictions, or audit trail recording.
Disaster Recovery – with no control over physical hardware, clients do not have hardware redundancy or isolated backups, which can mean no DR capability at all.
Supplier Lock-in – public clouds tend to be proprietary, so switching providers is resource intensive and costly, and may even be out of the question.
Dependability – if the cloud provider goes out of business you could lose access to your applications or data, and possibly even your backups.
Public Cloud Services