Why can a web site disappear from 'Top Sites' Categories without warning?

Why can a web site disappear from 'Top Sites' Categories without warning?

ShinyStat can exclude from 'Top Sites' anybody who do not comply to the terms and conditions of service.
Please make sure that:

• • The ShinyStat Free icon/counter is visible on the page registered to the service

• • The ShinyStat Free code is inserted in your web site homepage only

• • The URL indicated in the Setting section in the 'User information' page corresponds exactly to the one of the page containing the ShinyStat Free code

• • The URL registered to the service is correctly indicated and allows immediate access to the tracked page. This to guarantee any verifications against the specific topic

• The adult-only web sites are included in the proper category

Once the appropriate changes have been made, the user can ask for the inclusion into 'Top Sites' by filling the required form.