With the advent of cloud everything can be easy transformed in to 'as a service' services
It all started as SAAS(software as a service) which we all know about a great example will be an accounting software installed on Internet which charges according to number of users using the software.
Then we have IAAS(Infrastructure as a service) In which service providers still manage virtualization, servers, hard drives, storage, and networking where as users are responsible for managing their application and they also Install their softwares required to support their application.
Then comes Platform as a service (PaaS) In which service providers manage both hardware and software so that users can directly run their applications on them. PaaS frees users from having to install hardware and software to develop or run a new application.
Now comes DBaaS which provides Database in cloud for you and as a service in which you dunt have the headache of selecting and installing hardware and software for your backend Database you won't be needing database admins as well to maintain them.
No worries about installing and selecting hardware and software for your database to run.
No need of team to manage your database.
No worries about scaling.
No worries about performance tunings and configurations.
You dun't have to build database from scratch with all the tuning and configurations.
Your database software versions will be automatically updated you dunt have to update it manually as well.
No worries about backups.
If you are a pure tech company mostly all databases work fine unless it needs to scale heavily and it requires little maintainence as well If you dont want to get your hands dirty with tech then you can try out DBaaS.
Cutomization will be difficult lets say if you need a front end application which works well with a particular backend database only ,then it can create huge problems.
Your data is not directly controlled by you especially if its very critical data.
The costs can rise once you achieve scale because once you grow enough its better to manage a db by yourself only.
You will have to do a detailed analysis of the features provided by each and every DBaaS provider because DB is the heart of everything if your DBaaS provider is bad you will suffer badly.
A detailed analysis of all the features provided by each and every DBaaS provider and price comparisons also check if the service provider has prior legitimate experience in providing a DBaaS service.
Take a small trial dun't put all money at once test the waters first else if you will end up loosing your money if the service doesnt meet your requirements.
You can checkout Amazon RDS,Amazon SimpleDB and Google's big query(its more like a datawarehouse)