Is there a limit of widgets with the same widget id?



I am working on a CMS where I want the user/client to put only his twitter username to generate a widget of his timeline.
I know it is possible to do it using the same widget id for every timeline, and override its values with:
href="" data-screen-name="twitter_username"
but is there a limit of any kind? like number of embedded widgets with the same id, number of requests a single widget id can make in an interval, etc…