I have similar terms for my clients. However each service is independant of the other. Clients are never obligated to maintain hosting or maintenace with my company. I do require that I and respective companies retain rights to the coding & original design used for the site.
I have run into situations where my design etc. has been credited by another designer. This designer then acquires new clients as a result of my work. If a client wishes another company/person to maintain the site they are required to state "Site maintained by.." rather than stating developed by...
It is a lot of work to create websites according to a clients wishes. I will never feel it is right for someone else to take credit. In order to protect my work I have to require agreement to my terms.

...the client is automatically assigned rights to use as a web site the design, graphics, and text contained in the finished assembled web site. Rights to source code, work-up files, and computer programs are specifically not transferred to the client, and remain the property of their respective owners.

This works both ways... if I take over someone elses site I require permissions and will never state I developed the site.

Due to the number of unethical web developers many companies are forced to create terms that may seem unreasonable.

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Website consulting and design for...
small business, home based companies, personal or hobby websites
http://twopooches.com/