Some exhibit/booth areas are staffed by knowledgeable people who are happy to answer questions, chat and/or listen to ideas for using or improving their products.
> no base point to start a conversation
How about the topic of the talk?
If you ask a question during Q&A, others may be interested and approach you to follow up.
> like a dating site except with no bio
Conference speakers typically have public bios and photos, which helps with hallway recognition. Those who are open to talking can often be found in a small group, which can be joined via topical comment/question.