For one, Twitter is a "real turnaround project."
"We've covered Twitter for some time, and we can see some of the issues that Twitter has fundamentally. The issues with growth, the issues with decelerating revenue per issue, the issues with leadership that has turned over quite a bit," he said.
And while some may view a Twitter-Disney deal as a potential sports integration, with Disney's ESPN pairing well with Twitter live-streaming games, DiClemente has concerns. That's because deals with some of the pro-sports leagues require third-party distribution, and that means Disney could wind up spending more on fees and licensing, he explained.
He thinks Disney would be better looking into something in the video game or content space, noting that historically, media acquisitions of tech companies have not panned out very well.
Meanwhile, Disney isn't the only name being mentioned in connection with Twitter. Sources have told CNBC that Microsoft, Salesforce.com and Google are also potential suitors.
However, DiClemente doesn't see Google as a "great strategic fit" either.
"[I] don't mean to be a Debbie Downer on the potential for a big, blockbuster-hyped acquisition, but it could be another suitor like Microsoft, like Salesforce, who sees the virtue in extending their portfolio to social," he said.
— CNBC's David Faber contributed to this report.
Disclosures: Nomura has received compensation for non-investment banking services/products in the past 12 months from GOOGL. Nomura holds 1 percent or more of common equity securities of TWTR.