No, but relay operators will be forced to implement some sort.of rate limiting of they face a serious level of DDoS.

The free scrapeability of Nostr is a privacy concern though. Especially mm if people use the same identity for everything: Notes/Zaps, markets, Highlighter, Nests, Blogging etc etc.

Perfect fodder for analytics companies.

Especially since most Nostr users reuse their Twitter identity, for credibility reasons