Demerits of SharePoint online Office 365.

Following are  Missing (Demerits and Drawbacks ) Features/Services in SharePoint Online (365) :

1.) No  Central Administration but there is an “SharePoint Admin Center” .
2.) There is no Web Application Management / Managed Paths. All sites, other than the public and top level team site, must exist under the “.sharepoint.com/sites/” area
3.) You can only create Sandbox and App model solutions.There is no full Trust Solutions   3^rd party solutions would need to be in this format.
4.) Cross site publishing is not available in the online version .Cross-site publishing is a new publishing method that lets you create and maintain content in one or more authoring site collections and publish this content in one or more publishing site collections by using Search Web Parts. Cross-site publishing complements the already existing publishing method, author-in-place, where you use a single site collection to author content and make it available to readers of your site.
5.) Content by search  feature which allows content to be displayed in a web part via search is not there in the online version
6.) Following Services are not available in SharePoint Online:

• Access Services 2010
• PerformancePoint Service
• PowerPoint Automation Service
• State Service
• User and Health Data Collection Service*
  *(Office 365 provides separate health info in admin center)
• Word Automation Service
• Work Management Service
• Microsoft Foundation Subscription Settings Service

Sites Types

• Single public facing site
• Multiple internal/private sites (top level is a Team Site).
  *There are no web applications.  All sites must exist under a single web application using separate site collections

Data Storage Limitations

• Tenant storage: 10 GB + 500 MB per subscribed user + additional storage purchased.  For example, if you have 10,000 users, the base storage allocation is approximately 5 Terabytes (10 GB + 500 MB * 10,000 users).
• Site collection: Hard limit of 100GB
• Overall subscription limit: 25TB

External Users

Per MS: “An external user is a person who has been granted access to your SharePoint Online site, but who is not a licensed user within your organization. External users are users who are not employees, contractors, or onsite agents for either you or your affiliates.”

• Maximum number of external users: 10,000
• External users cannot create their own My Sites or OneDrive Pro
• Cannot change their profile, edit picture or see tasks
• Cannot be an administrator for a site collection
• Cannot access search center or execute searches against “everything”

Branding Limitations

Adding a custom design to the internal site “Team Site” is a bit counter intuitive.  The option to select a MasterPage is not available under “Site Settings.”  You must upload the MasterPage to the MasterPage gallery, along with a “Preview” file.  Then, you must create a “Composed” look.  From there it will be available under the “Change the Look” feature.  I hope to detail this out more in a future post.

Other Notable Limitations

• Migration must be done remotely :  Migration is painful. If you have an existing SharePoint site, moving it to Office 365 is a lot less nice than you’d like. Microsoft don’t provide their own tools to do this, there are external tools which we used, which help, but it takes a long time and the migration isn’t perfect.
  
  Migration is painful. If you have an existing SharePoint site, moving it to Office 365 is a lot less nice than you’d like. Microsoft don’t provide their own tools to do this, there are external tools which we used, which help, but it takes a long time and the migration isn’t perfect. - See more at: http://blog.sharepointlearn.com/2011/11/03/sharepoint-in-office-365-the-good-the-bad-the-brilliant-and-the-ugly/#sthash.bKR14CEk.dpuf
• Disks cannot be shipped
• Cannot control upgrade schedule
• BCS security concerns about opening local data up to the cloud
• You are limited in the number of email recipients you can send to. Although more an Exchange feature than a SharePoint one, there is a limit to the number of email recipients that you can send from a single mailbox; this is 500 a day on the more basic Office 365 packages and 1500 a day for enterprises. So if you want to make an announcement or send out a newsletter, you are limited to the number of people you can send it to. - See more at: http://blog.sharepointlearn.com/2011/11/03/sharepoint-in-office-365-the-good-the-bad-the-brilliant-and-the-ugly/#sthash.bKR14CEk.dpuf
   You are limited in the number of email recipients you can send to. Although more an Exchange feature than a SharePoint one, there is a limit to the number of email recipients that you can send from a single mailbox; this is 500 a day on the more basic Office 365 packages and 1500 a day for enterprises. So if you want to make an announcement or send out a newsletter, you are limited to the number of people you can send it to. 
• Lists, libraries and wikis with more than 5,000 entries don’t seem to work properly. In theory, SharePoint Online can have millions of entries in a list or library, but in practice in the current release, if you have more than 5,000 you don’t seem to be able to use the library (e.g. cannot set permissions).  
• You can’t open PDFs, you have to download them before opening. Apparently due to security concerns, if you have PDFs that you want people to open on your site, they can’t click and open them directly, you have to save them on your local computer first and then view

.