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> The commercial online assessment services currently offered by PV installation companies require the input of personal details such as email addresses which **hook in** clients. 
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"Hook in" seems like a bit of a colloquialism, is there a better term for this? To me, the noun hook in the context of "marketing hook" seems alright, but as a verb it seems rather casual.

I want to convey the idea that once the consumer uses this service and provides any personal information, they are stuck or trapped in a loop and are forced to have additional contact or dealings with the business. 

I looked up in a thesaurus and came up with snared or lured, but does anyone have any better suggestions please?