This is another issue I have, any reason as to why?
When you flash CM7, you have to also flash the gapps package, and twitter and youtube have to be downloaded from the market. I nuked youtube, but I did download and install twitter, and have a choice of 2 widgets.
Well it is not CM7 per se, as I have the widgets. You can try going into the settings/applications/downloaded and nuke the data for them, or try uninstalling and reinstalling.