Hi.  I've see twice this year two different companies either already or planning on having ssas and ssrs running on the same server.  Is there a good reason that folks do this? 

If you have the hardware, there is no reason you cannot run everything on a single server.

thx but they split off ssis and some ssrs supporting tables to two other servers so i'm wondering if there is a tendency out there to couple just these two for some reason.

They are completely independent services.  There is no interaction or dependency on them at all.

As Tom Phillips stated earlier, SSAS and SSRS are independent services.  The only real issue that I can think of is having enough resources on the server during peak times to support both services.

There are other reasons why you may want to have multiple SQL Server services on the same server.  The biggest one is licensing.  If you have each service on a separate server, then each server should be a separate license.  Now that you have more servers, you have more servers to fail over in case of planned/unplanned outages.  In addition, if your network is really slow, then query requests between the SSRS and SSAS server may take more time.  In other cases, Kerberos can't be set up correctly, so Windows user authentication between servers doesn't work.  A quick solution to the authentication issue is just to have everything on a single server.

Those are a few reasons that I can think off the top of my head.