I would rewrite the sentence as follows:
1. Surveys note, however, that the elderly are frequent victims of certain types of crime, like purse-snatching.
i.e. with a comma after "note", and with "crime" in the singular.
"Maybe" is an adverb; you use it when you're not sure if something is true or will happen, e.g.
2. Maybe I'll go for a drink tonight. [I'm not sure if I will go for a drink.]
3. Is that the girl you went out with yesterday? — Well, maybe... [I'm not sure if it's the girl I went out with yesterday.]
"May be" is verbal, e.g.
4. She may be the girl I saw yesterday.
5. I may be going for a drink tonight.
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