READ THIS SOLUTION
None of the above suggested solutions is helpful at all honestly. Even looping through the dataSource looking for a match can be bad, because its possible you have two different records with same 'name'.
And dropDownList is just NOT desired, nor is multiSelect!
Quite honestly, the lack of dataValueField is inexcusable. Breaks pattern of other widgets and for NO good reason. Telerik should fix this, not argue that you should use a different widget.
BULLETPROOF SOLUTION FOR NOW
This is just an example that assumes some things about your datasource, but holds true no matter what datasource you use.
"your data source url here"
// <-- this doesn't work, but should!
'<span data-recordid="#= id #"> #= name #</span>'
// here we just use a template and put the id as data on the span wrapping the name
// this is how you grab the id from the item selected
Never used the code formatter of this forum, hopefully it adds indents.