With Facebook shares trading close to their $38 offer price and revelations that retail investors got a larger-than-expected slice of the $18.4 billion IPO, market watchers are questioning whether the social network’s debut was overhyped — not just in the media, but in the investor community.

Buy-side anticipation of a huge Day One price pop was high, and yet as of lunch time on Friday, Facebook shares hadn’t crested $45.

Experienced bankers say that with a new issue of this size, moving the shares beyond the single-digit percentage range can be tough, and that Morgan Stanley , the lead bookrunner on the deal, has done an admirable job at keeping the stock trading in relatively stable condition.

GM , for instance, which was an $18.1 billion IPO, only traded a few percentage points above its new issue price on its first day of trading late in 2010. Prior to the first day of trading, bankers said they didn’t expect a more than 10% upsurge on day one, given the deal’s size.

However, with anecdotal reports that some institutional investors got more shares than they were expecting, and new revelations that, according to two people close to the matter, the retail allocation of Facebook IPO shares was more than 20 percent, marking an all-time high for a new issue, some market participants are wondering whether the investor excitement toward the deal was overplayed earlier this week.

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