This problem is addressed in ArcGIS 8.1 Service Pack 1. See the Related Information section to download this pack.
If the TIN Builder dialog is used to create a TIN, it may add tag values even though they weren't requested.
If points were input to the output TIN, it will have node tag values set to the point OIDs. If polygons were used the TIN will have triangle tag values set to the polygon OIDs.
This is a known issue.